How to develop android apps?
there is many ways... [ Xamarin(C#), B4A(basic), Eclipse & Android Studio(Java), Kotlin] I suggest you learn Java language and work with Android studio,,, Good Luck
learn Java (and I mean learn it WELL), and download Android Studio IDE. the inner workings of android app rely heavily on the Java language. also, google and sign up for any tutorials regarding Android App Development (check out the website 'Udemy', they're pretty good from what i hear)