How can I create applications

Question

How to design apps

Answer 1

The official way to make Android apps: With Android Studio.

But if you want to make games, you have a lot of game engines like:
-Unity: Make 2D and 3D games for free, used to make great games like The Forest or Rust. It works with C# language.
-GameMaker Studio: Make 2D (Or basic 3D) games for free(With a limited version), used to make games like Undertale. It has its own programming language, but with a JavaScript-like syntax.

And you have two great options to make apps for android in android:
-Java N-Ide: Make android apps for free with a simple but complete interface.
-AIDE: Make android apps with the best option, it have gui maker like Android Studio, but isn't free.

If you want to make apps with Android Studio, Java N-IDE or AIDE, it use Java.

Answer 2

Design for ui? or design for businesse logics ?