I think learning Android in 2018 is very exciting now as Google officially supports Kotlin and introduction of new set of libraries such as Android Jetpack.
https://developer.android.com/jetpack/
By following newly introduced jetpack, you could avoid most of the deprecated libraries.
And going through the google architecture blueprints repo and sample https://github.com/googlesamples/android-architecture
will help you understand how you should approach to your new apps development and help you get started in a right way.
26, I learned to swim effectively and effortlessly few weeks ago and still learning and practicing. And learned Android Architecture Components, Dependency Injection and Firebase as my profession is android developer.
And going through the google architecture blueprints repo and sample https://github.com/googlesamples/android-architecture will help you understand how you should approach to your new apps development and help you get started in a right way.