Optimized language, themes, colors.

Added splashscreen, SplashActivity.

app/src/main/res/layout/activity_splash.xml

@@ -1,8 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
-    android:layout_height="match_parent"
-    tools:context=".SplashActivity">
+    android:layout_height="match_parent">
 
 </androidx.constraintlayout.widget.ConstraintLayout>

app/src/main/res/layout/app_bar_main.xml

@@ -29,6 +29,6 @@
         android:layout_gravity="bottom|end"
         android:layout_margin="@dimen/fab_margin"
         app:srcCompat="@android:drawable/ic_dialog_email"
-        android:contentDescription="TODO" />
+        android:contentDescription="@string/fab" />
 
 </androidx.coordinatorlayout.widget.CoordinatorLayout>

app/src/main/res/layout/content_main.xml

@@ -7,7 +7,7 @@
     app:layout_behavior="@string/appbar_scrolling_view_behavior"
     tools:showIn="@layout/app_bar_main">
 
-    <fragment
+    <androidx.fragment.app.FragmentContainerView
         android:id="@+id/nav_host_fragment"
         android:name="androidx.navigation.fragment.NavHostFragment"
         android:layout_width="match_parent"

app/src/main/res/layout/fold_layout_head.xml

@@ -15,6 +15,7 @@
         android:layout_width="0dp"
         android:layout_height="20dp"
         android:layout_weight="1"
+        android:gravity="center"
         android:textAlignment="center"
         android:textSize="20sp"
         android:textColor="@color/app_theme" />
@@ -25,7 +26,7 @@
         android:layout_height="40dp"
         android:layout_weight="6"
         android:gravity="center_vertical"
-        android:textColor="@color/black"
+        android:textColor="@color/app_text_theme"
         android:textSize="18sp" />
 
     <ImageView
@@ -33,5 +34,6 @@
         android:layout_width="0dp"
         android:layout_height="15dp"
         android:layout_weight="1"
-        app:srcCompat="@drawable/right_to_down_arrow" />
+        app:srcCompat="@drawable/right_to_down_arrow"
+        android:contentDescription="@string/arrow_icon" />
 </LinearLayout>

app/src/main/res/layout/fragment_home.xml

@@ -12,6 +12,7 @@
         android:id="@+id/fold_layouts_linear_layout"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
+        android:paddingTop="10dp"
         android:paddingBottom="10dp"
         android:orientation="vertical">
     </LinearLayout>