How to work with graphics in Android Studio?

Question

android studio

I set a goal for myself to learn how to code for android. I use Android Studio as a development tool. Literally from the very start, I ran into a number of questions.
For example, I can’t figure out how to properly set the background for an application.
I have a 16:9 image with dead zones to adapt to 4:3, but if I set it as the background for a RelativeLayout, it shrinks and gets distorted. If I set it as an ImageView background with the CentCrop attribute, it still compresses.
Explain how to do it right.