I started developing android apps, any advice?

Question

I actually focusing on tools type of android app such as soft keyboard and others so i want to know what i need to know to make good and unique apps.
Note that i am web developer, and i am new with android development.
This is my first app on github
https://github.com/Dteam-dz/Flash_Calculate

Answer 1

Best guide for begginer

https://developer.android.com/guide

Answer 2

If you are on JavaScript tech stack, use ReactNative