Where to start?
I write this article from perspective of Java programmer. So I assume that you already know Java and Gradle.
Before you start making mobile apps, it’s good to know Kotlin. I recommend you to try out Kotlin Koans. It’s an easy to follow series of exercises that will help you have a grasp of programming in Kotlin.
A good beginning with a mobile application development is the Build your first app guide. It’s short, but gets you started with Android environment.
More thorough but still basic tutorial series is the Android Developer Fundamentals Course. It will overlap a little with the previous guide, but I think it’s good to have a little recap. After completing it, you will know how to make an Android application with SQLite database.
The next logical step is the Advanced Android Developer Course. Treat it like part two to the fundamentals course.
Lastly, you should find some open-source Android project and contribute to it. If you don’t find any, make one yourself.
If you do anything with the Room library, you will encounter at coroutines. To better understand them, it is worth to check yet another guide prepared by Google.