diff --git a/app/src/main/res/layout/client_not_signed.xml b/app/src/main/res/layout/client_not_signed.xml
index e3b0b4e..133f71f 100644
--- a/app/src/main/res/layout/client_not_signed.xml
+++ b/app/src/main/res/layout/client_not_signed.xml
@@ -9,31 +9,42 @@
     tools:layout_editor_absoluteX="11dp"
     tools:layout_editor_absoluteY="107dp">
 
-    <Button
+    <com.google.android.material.button.MaterialButton
         android:id="@+id/Qprev"
-        android:tag="previous"
-        android:layout_width="180dp"
-        android:layout_height="60dp"
-        android:textSize="30sp"
+        android:layout_width="@dimen/nav_btn_size"
+        android:layout_height="@dimen/nav_btn_size"
+        android:layout_marginStart="20dp"
+        android:layout_marginBottom="16dp"
+        android:text=""
+        android:textAllCaps="false"
+        app:icon="@drawable/ic_chevron_left"
+        app:iconTint="@color/btn_nav_left_icon_tint"
+        app:iconSize="@dimen/nav_icon_size"
+        app:iconPadding="0dp"
+        app:cornerRadius="999dp"
+        app:backgroundTint="@color/btn_nav_left_tint"
+        app:rippleColor="@color/btn_nav_left_ripple"
         app:layout_constraintBottom_toBottomOf="parent"
-        app:layout_constraintEnd_toEndOf="parent"
-        app:layout_constraintHorizontal_bias="0.056"
-        app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toTopOf="parent"
-        app:layout_constraintVertical_bias="0.976" />
+        app:layout_constraintStart_toStartOf="parent" />
 
-    <Button
+    <!-- Weiter -->
+    <com.google.android.material.button.MaterialButton
         android:id="@+id/Qnext"
-        android:tag="next"
-        android:layout_width="180dp"
-        android:layout_height="60dp"
-        android:textSize="30sp"
+        android:layout_width="@dimen/nav_btn_size"
+        android:layout_height="@dimen/nav_btn_size"
+        android:layout_marginEnd="20dp"
+        android:layout_marginBottom="16dp"
+        android:text=""
+        android:textAllCaps="false"
+        app:icon="@drawable/ic_chevron_right"
+        app:iconTint="@color/btn_nav_right_icon_tint"
+        app:iconSize="@dimen/nav_icon_size"
+        app:iconPadding="0dp"
+        app:cornerRadius="999dp"
+        app:backgroundTint="@color/btn_nav_right_tint"
+        app:rippleColor="@color/btn_nav_right_ripple"
         app:layout_constraintBottom_toBottomOf="parent"
-        app:layout_constraintEnd_toEndOf="parent"
-        app:layout_constraintHorizontal_bias="0.943"
-        app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toTopOf="parent"
-        app:layout_constraintVertical_bias="0.976" />
+        app:layout_constraintEnd_toEndOf="parent" />
 
 
     <EditText
diff --git a/app/src/main/res/layout/date_spinner.xml b/app/src/main/res/layout/date_spinner.xml
index c43eea1..e7d37c9 100644
--- a/app/src/main/res/layout/date_spinner.xml
+++ b/app/src/main/res/layout/date_spinner.xml
@@ -111,48 +111,41 @@
         app:layout_constraintTop_toBottomOf="@id/date_spinner_year"
         app:layout_constraintWidth_percent="0.32" />
 
-    <Button
+    <com.google.android.material.button.MaterialButton
         android:id="@+id/Qprev"
-        android:layout_width="0dp"
-        android:layout_height="0dp"
-        android:layout_marginEnd="70dp"
-        android:layout_marginBottom="12dp"
-        android:autoSizeMaxTextSize="48sp"
-        android:autoSizeMinTextSize="12sp"
-        android:autoSizeStepGranularity="2sp"
-        android:autoSizeTextType="uniform"
-        android:gravity="center"
-        android:paddingStart="12dp"
-        android:paddingEnd="12dp"
-        android:tag="previous"
+        android:layout_width="@dimen/nav_btn_size"
+        android:layout_height="@dimen/nav_btn_size"
+        android:layout_marginStart="20dp"
+        android:layout_marginBottom="16dp"
+        android:text=""
+        android:textAllCaps="false"
+        app:icon="@drawable/ic_chevron_left"
+        app:iconTint="@color/btn_nav_left_icon_tint"
+        app:iconSize="@dimen/nav_icon_size"
+        app:iconPadding="0dp"
+        app:cornerRadius="999dp"
+        app:backgroundTint="@color/btn_nav_left_tint"
+        app:rippleColor="@color/btn_nav_left_ripple"
         app:layout_constraintBottom_toBottomOf="parent"
-        app:layout_constraintEnd_toStartOf="@id/Qnext"
-        app:layout_constraintHeight_percent="0.07"
-        app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toTopOf="parent"
-        app:layout_constraintVertical_bias="1.0"
-        app:layout_constraintWidth_percent="0.30" />
+        app:layout_constraintStart_toStartOf="parent" />
 
-    <Button
+    <!-- Weiter -->
+    <com.google.android.material.button.MaterialButton
         android:id="@+id/Qnext"
-        android:layout_width="0dp"
-        android:layout_height="0dp"
-        android:layout_marginBottom="12dp"
-        android:layout_marginStart="70dp"
-        android:autoSizeMaxTextSize="48sp"
-        android:autoSizeMinTextSize="12sp"
-        android:autoSizeStepGranularity="2sp"
-        android:autoSizeTextType="uniform"
-        android:gravity="center"
-        android:paddingStart="12dp"
-        android:paddingEnd="12dp"
-        android:tag="next"
+        android:layout_width="@dimen/nav_btn_size"
+        android:layout_height="@dimen/nav_btn_size"
+        android:layout_marginEnd="20dp"
+        android:layout_marginBottom="16dp"
+        android:text=""
+        android:textAllCaps="false"
+        app:icon="@drawable/ic_chevron_right"
+        app:iconTint="@color/btn_nav_right_icon_tint"
+        app:iconSize="@dimen/nav_icon_size"
+        app:iconPadding="0dp"
+        app:cornerRadius="999dp"
+        app:backgroundTint="@color/btn_nav_right_tint"
+        app:rippleColor="@color/btn_nav_right_ripple"
         app:layout_constraintBottom_toBottomOf="parent"
-        app:layout_constraintEnd_toEndOf="parent"
-        app:layout_constraintHeight_percent="0.07"
-        app:layout_constraintStart_toEndOf="@id/Qprev"
-        app:layout_constraintTop_toTopOf="parent"
-        app:layout_constraintVertical_bias="1.0"
-        app:layout_constraintWidth_percent="0.30" />
+        app:layout_constraintEnd_toEndOf="parent" />
 
 </androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/app/src/main/res/layout/glass_scale_question.xml b/app/src/main/res/layout/glass_scale_question.xml
index e98bb03..dbf0a50 100644
--- a/app/src/main/res/layout/glass_scale_question.xml
+++ b/app/src/main/res/layout/glass_scale_question.xml
@@ -74,48 +74,41 @@
     </ScrollView>
 
     <!-- Buttons unten -->
-    <Button
+    <com.google.android.material.button.MaterialButton
         android:id="@+id/Qprev"
-        android:layout_width="0dp"
-        android:layout_height="0dp"
-        android:layout_marginEnd="70dp"
-        android:layout_marginBottom="12dp"
-        android:autoSizeMaxTextSize="48sp"
-        android:autoSizeMinTextSize="12sp"
-        android:autoSizeStepGranularity="2sp"
-        android:autoSizeTextType="uniform"
-        android:gravity="center"
-        android:paddingStart="12dp"
-        android:paddingEnd="12dp"
-        android:tag="previous"
+        android:layout_width="@dimen/nav_btn_size"
+        android:layout_height="@dimen/nav_btn_size"
+        android:layout_marginStart="20dp"
+        android:layout_marginBottom="16dp"
+        android:text=""
+        android:textAllCaps="false"
+        app:icon="@drawable/ic_chevron_left"
+        app:iconTint="@color/btn_nav_left_icon_tint"
+        app:iconSize="@dimen/nav_icon_size"
+        app:iconPadding="0dp"
+        app:cornerRadius="999dp"
+        app:backgroundTint="@color/btn_nav_left_tint"
+        app:rippleColor="@color/btn_nav_left_ripple"
         app:layout_constraintBottom_toBottomOf="parent"
-        app:layout_constraintEnd_toStartOf="@id/Qnext"
-        app:layout_constraintHeight_percent="0.07"
-        app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toTopOf="parent"
-        app:layout_constraintVertical_bias="1.0"
-        app:layout_constraintWidth_percent="0.30" />
+        app:layout_constraintStart_toStartOf="parent" />
 
-    <Button
+    <!-- Weiter -->
+    <com.google.android.material.button.MaterialButton
         android:id="@+id/Qnext"
-        android:layout_width="0dp"
-        android:layout_height="0dp"
-        android:layout_marginBottom="12dp"
-        android:layout_marginStart="70dp"
-        android:autoSizeMaxTextSize="48sp"
-        android:autoSizeMinTextSize="12sp"
-        android:autoSizeStepGranularity="2sp"
-        android:autoSizeTextType="uniform"
-        android:gravity="center"
-        android:paddingStart="12dp"
-        android:paddingEnd="12dp"
-        android:tag="next"
+        android:layout_width="@dimen/nav_btn_size"
+        android:layout_height="@dimen/nav_btn_size"
+        android:layout_marginEnd="20dp"
+        android:layout_marginBottom="16dp"
+        android:text=""
+        android:textAllCaps="false"
+        app:icon="@drawable/ic_chevron_right"
+        app:iconTint="@color/btn_nav_right_icon_tint"
+        app:iconSize="@dimen/nav_icon_size"
+        app:iconPadding="0dp"
+        app:cornerRadius="999dp"
+        app:backgroundTint="@color/btn_nav_right_tint"
+        app:rippleColor="@color/btn_nav_right_ripple"
         app:layout_constraintBottom_toBottomOf="parent"
-        app:layout_constraintEnd_toEndOf="parent"
-        app:layout_constraintHeight_percent="0.07"
-        app:layout_constraintStart_toEndOf="@id/Qprev"
-        app:layout_constraintTop_toTopOf="parent"
-        app:layout_constraintVertical_bias="1.0"
-        app:layout_constraintWidth_percent="0.30" />
+        app:layout_constraintEnd_toEndOf="parent" />
 
 </androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/app/src/main/res/layout/last_page.xml b/app/src/main/res/layout/last_page.xml
index 708e0c3..5f77198 100644
--- a/app/src/main/res/layout/last_page.xml
+++ b/app/src/main/res/layout/last_page.xml
@@ -5,27 +5,23 @@
     android:layout_width="match_parent"
     android:layout_height="match_parent">
 
-    <Button
+    <com.google.android.material.button.MaterialButton
         android:id="@+id/Qprev"
-        android:layout_width="0dp"
-        android:layout_height="0dp"
-        android:layout_marginEnd="70dp"
-        android:layout_marginBottom="12dp"
-        android:autoSizeMaxTextSize="48sp"
-        android:autoSizeMinTextSize="12sp"
-        android:autoSizeStepGranularity="2sp"
-        android:autoSizeTextType="uniform"
-        android:gravity="center"
-        android:paddingStart="12dp"
-        android:paddingEnd="12dp"
-        android:tag="previous"
+        android:layout_width="@dimen/nav_btn_size"
+        android:layout_height="@dimen/nav_btn_size"
+        android:layout_marginStart="20dp"
+        android:layout_marginBottom="16dp"
+        android:text=""
+        android:textAllCaps="false"
+        app:icon="@drawable/ic_chevron_left"
+        app:iconTint="@color/btn_nav_left_icon_tint"
+        app:iconSize="@dimen/nav_icon_size"
+        app:iconPadding="0dp"
+        app:cornerRadius="999dp"
+        app:backgroundTint="@color/btn_nav_left_tint"
+        app:rippleColor="@color/btn_nav_left_ripple"
         app:layout_constraintBottom_toBottomOf="parent"
-        app:layout_constraintEnd_toStartOf="@id/Qfinish"
-        app:layout_constraintHeight_percent="0.07"
-        app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toTopOf="parent"
-        app:layout_constraintVertical_bias="1.0"
-        app:layout_constraintWidth_percent="0.30" />
+        app:layout_constraintStart_toStartOf="parent" />
 
     <Button
         android:id="@+id/Qfinish"
diff --git a/app/src/main/res/layout/multi_check_box_question.xml b/app/src/main/res/layout/multi_check_box_question.xml
index 727e7ff..4d616c8 100644
--- a/app/src/main/res/layout/multi_check_box_question.xml
+++ b/app/src/main/res/layout/multi_check_box_question.xml
@@ -9,49 +9,42 @@
     tools:layout_editor_absoluteX="11dp"
     tools:layout_editor_absoluteY="107dp">
 
-    <Button
+    <com.google.android.material.button.MaterialButton
         android:id="@+id/Qprev"
-        android:layout_width="0dp"
-        android:layout_height="0dp"
-        android:layout_marginEnd="70dp"
-        android:layout_marginBottom="12dp"
-        android:autoSizeMaxTextSize="48sp"
-        android:autoSizeMinTextSize="12sp"
-        android:autoSizeStepGranularity="2sp"
-        android:autoSizeTextType="uniform"
-        android:gravity="center"
-        android:paddingStart="12dp"
-        android:paddingEnd="12dp"
-        android:tag="previous"
+        android:layout_width="@dimen/nav_btn_size"
+        android:layout_height="@dimen/nav_btn_size"
+        android:layout_marginStart="20dp"
+        android:layout_marginBottom="16dp"
+        android:text=""
+        android:textAllCaps="false"
+        app:icon="@drawable/ic_chevron_left"
+        app:iconTint="@color/btn_nav_left_icon_tint"
+        app:iconSize="@dimen/nav_icon_size"
+        app:iconPadding="0dp"
+        app:cornerRadius="999dp"
+        app:backgroundTint="@color/btn_nav_left_tint"
+        app:rippleColor="@color/btn_nav_left_ripple"
         app:layout_constraintBottom_toBottomOf="parent"
-        app:layout_constraintEnd_toStartOf="@id/Qnext"
-        app:layout_constraintHeight_percent="0.07"
-        app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toTopOf="parent"
-        app:layout_constraintVertical_bias="1.0"
-        app:layout_constraintWidth_percent="0.30" />
+        app:layout_constraintStart_toStartOf="parent" />
 
-    <Button
+    <!-- Weiter -->
+    <com.google.android.material.button.MaterialButton
         android:id="@+id/Qnext"
-        android:layout_width="0dp"
-        android:layout_height="0dp"
-        android:layout_marginBottom="12dp"
-        android:layout_marginStart="70dp"
-        android:autoSizeMaxTextSize="48sp"
-        android:autoSizeMinTextSize="12sp"
-        android:autoSizeStepGranularity="2sp"
-        android:autoSizeTextType="uniform"
-        android:gravity="center"
-        android:paddingStart="12dp"
-        android:paddingEnd="12dp"
-        android:tag="next"
+        android:layout_width="@dimen/nav_btn_size"
+        android:layout_height="@dimen/nav_btn_size"
+        android:layout_marginEnd="20dp"
+        android:layout_marginBottom="16dp"
+        android:text=""
+        android:textAllCaps="false"
+        app:icon="@drawable/ic_chevron_right"
+        app:iconTint="@color/btn_nav_right_icon_tint"
+        app:iconSize="@dimen/nav_icon_size"
+        app:iconPadding="0dp"
+        app:cornerRadius="999dp"
+        app:backgroundTint="@color/btn_nav_right_tint"
+        app:rippleColor="@color/btn_nav_right_ripple"
         app:layout_constraintBottom_toBottomOf="parent"
-        app:layout_constraintEnd_toEndOf="parent"
-        app:layout_constraintHeight_percent="0.07"
-        app:layout_constraintStart_toEndOf="@id/Qprev"
-        app:layout_constraintTop_toTopOf="parent"
-        app:layout_constraintVertical_bias="1.0"
-        app:layout_constraintWidth_percent="0.30" />
+        app:layout_constraintEnd_toEndOf="parent" />
 
     <!-- ScrollView füllt den Raum zwischen Frage und Buttons -->
     <ScrollView
diff --git a/app/src/main/res/layout/string_spinner.xml b/app/src/main/res/layout/string_spinner.xml
index 5fa05d1..489006d 100644
--- a/app/src/main/res/layout/string_spinner.xml
+++ b/app/src/main/res/layout/string_spinner.xml
@@ -15,49 +15,42 @@
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintTop_toBottomOf="@id/question" />
 
-    <Button
+    <com.google.android.material.button.MaterialButton
         android:id="@+id/Qprev"
-        android:layout_width="0dp"
-        android:layout_height="0dp"
-        android:layout_marginEnd="70dp"
-        android:layout_marginBottom="12dp"
-        android:autoSizeMaxTextSize="48sp"
-        android:autoSizeMinTextSize="12sp"
-        android:autoSizeStepGranularity="2sp"
-        android:autoSizeTextType="uniform"
-        android:gravity="center"
-        android:paddingStart="12dp"
-        android:paddingEnd="12dp"
-        android:tag="previous"
+        android:layout_width="@dimen/nav_btn_size"
+        android:layout_height="@dimen/nav_btn_size"
+        android:layout_marginStart="20dp"
+        android:layout_marginBottom="16dp"
+        android:text=""
+        android:textAllCaps="false"
+        app:icon="@drawable/ic_chevron_left"
+        app:iconTint="@color/btn_nav_left_icon_tint"
+        app:iconSize="@dimen/nav_icon_size"
+        app:iconPadding="0dp"
+        app:cornerRadius="999dp"
+        app:backgroundTint="@color/btn_nav_left_tint"
+        app:rippleColor="@color/btn_nav_left_ripple"
         app:layout_constraintBottom_toBottomOf="parent"
-        app:layout_constraintEnd_toStartOf="@id/Qnext"
-        app:layout_constraintHeight_percent="0.07"
-        app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toTopOf="parent"
-        app:layout_constraintVertical_bias="1.0"
-        app:layout_constraintWidth_percent="0.30" />
+        app:layout_constraintStart_toStartOf="parent" />
 
-    <Button
+    <!-- Weiter -->
+    <com.google.android.material.button.MaterialButton
         android:id="@+id/Qnext"
-        android:layout_width="0dp"
-        android:layout_height="0dp"
-        android:layout_marginBottom="12dp"
-        android:layout_marginStart="70dp"
-        android:autoSizeMaxTextSize="48sp"
-        android:autoSizeMinTextSize="12sp"
-        android:autoSizeStepGranularity="2sp"
-        android:autoSizeTextType="uniform"
-        android:gravity="center"
-        android:paddingStart="12dp"
-        android:paddingEnd="12dp"
-        android:tag="next"
+        android:layout_width="@dimen/nav_btn_size"
+        android:layout_height="@dimen/nav_btn_size"
+        android:layout_marginEnd="20dp"
+        android:layout_marginBottom="16dp"
+        android:text=""
+        android:textAllCaps="false"
+        app:icon="@drawable/ic_chevron_right"
+        app:iconTint="@color/btn_nav_right_icon_tint"
+        app:iconSize="@dimen/nav_icon_size"
+        app:iconPadding="0dp"
+        app:cornerRadius="999dp"
+        app:backgroundTint="@color/btn_nav_right_tint"
+        app:rippleColor="@color/btn_nav_right_ripple"
         app:layout_constraintBottom_toBottomOf="parent"
-        app:layout_constraintEnd_toEndOf="parent"
-        app:layout_constraintHeight_percent="0.07"
-        app:layout_constraintStart_toEndOf="@id/Qprev"
-        app:layout_constraintTop_toTopOf="parent"
-        app:layout_constraintVertical_bias="1.0"
-        app:layout_constraintWidth_percent="0.30" />
+        app:layout_constraintEnd_toEndOf="parent" />
 
     <TextView
         android:id="@+id/textView"
diff --git a/app/src/main/res/layout/value_spinner.xml b/app/src/main/res/layout/value_spinner.xml
index 82e9adf..4f07dc0 100644
--- a/app/src/main/res/layout/value_spinner.xml
+++ b/app/src/main/res/layout/value_spinner.xml
@@ -17,49 +17,42 @@
         app:layout_constraintVertical_bias="0.027"
         app:layout_constraintWidth_percent="0.70" />
 
-    <Button
+    <com.google.android.material.button.MaterialButton
         android:id="@+id/Qprev"
-        android:layout_width="0dp"
-        android:layout_height="0dp"
-        android:layout_marginEnd="70dp"
-        android:layout_marginBottom="12dp"
-        android:autoSizeMaxTextSize="48sp"
-        android:autoSizeMinTextSize="12sp"
-        android:autoSizeStepGranularity="2sp"
-        android:autoSizeTextType="uniform"
-        android:gravity="center"
-        android:paddingStart="12dp"
-        android:paddingEnd="12dp"
-        android:tag="previous"
+        android:layout_width="@dimen/nav_btn_size"
+        android:layout_height="@dimen/nav_btn_size"
+        android:layout_marginStart="20dp"
+        android:layout_marginBottom="16dp"
+        android:text=""
+        android:textAllCaps="false"
+        app:icon="@drawable/ic_chevron_left"
+        app:iconTint="@color/btn_nav_left_icon_tint"
+        app:iconSize="@dimen/nav_icon_size"
+        app:iconPadding="0dp"
+        app:cornerRadius="999dp"
+        app:backgroundTint="@color/btn_nav_left_tint"
+        app:rippleColor="@color/btn_nav_left_ripple"
         app:layout_constraintBottom_toBottomOf="parent"
-        app:layout_constraintEnd_toStartOf="@id/Qnext"
-        app:layout_constraintHeight_percent="0.07"
-        app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toTopOf="parent"
-        app:layout_constraintVertical_bias="1.0"
-        app:layout_constraintWidth_percent="0.30" />
+        app:layout_constraintStart_toStartOf="parent" />
 
-    <Button
+    <!-- Weiter -->
+    <com.google.android.material.button.MaterialButton
         android:id="@+id/Qnext"
-        android:layout_width="0dp"
-        android:layout_height="0dp"
-        android:layout_marginBottom="12dp"
-        android:layout_marginStart="70dp"
-        android:autoSizeMaxTextSize="48sp"
-        android:autoSizeMinTextSize="12sp"
-        android:autoSizeStepGranularity="2sp"
-        android:autoSizeTextType="uniform"
-        android:gravity="center"
-        android:paddingStart="12dp"
-        android:paddingEnd="12dp"
-        android:tag="next"
+        android:layout_width="@dimen/nav_btn_size"
+        android:layout_height="@dimen/nav_btn_size"
+        android:layout_marginEnd="20dp"
+        android:layout_marginBottom="16dp"
+        android:text=""
+        android:textAllCaps="false"
+        app:icon="@drawable/ic_chevron_right"
+        app:iconTint="@color/btn_nav_right_icon_tint"
+        app:iconSize="@dimen/nav_icon_size"
+        app:iconPadding="0dp"
+        app:cornerRadius="999dp"
+        app:backgroundTint="@color/btn_nav_right_tint"
+        app:rippleColor="@color/btn_nav_right_ripple"
         app:layout_constraintBottom_toBottomOf="parent"
-        app:layout_constraintEnd_toEndOf="parent"
-        app:layout_constraintHeight_percent="0.07"
-        app:layout_constraintStart_toEndOf="@id/Qprev"
-        app:layout_constraintTop_toTopOf="parent"
-        app:layout_constraintVertical_bias="1.0"
-        app:layout_constraintWidth_percent="0.30" />
+        app:layout_constraintEnd_toEndOf="parent" />
 
     <TextView
         android:id="@+id/textView"