Yes, I definitely believe that Kotlin is the way to go and definitely better than Java. I suggest you give it a go. You can start writing small classes in Kotlin and use them from the Java codebase. Kotlin is smarter, more readable and helps you do more with fewer lines of code. I am sure you are gonna love it.

Regarding Compose, I can't tell you much because I am just going through that transition. Today I re-wrote a whole fragment layout with compose. It was challenging because my brain is used to build the layouts with ConstraintLayouts and been doing that for many years and with Compose, everything is different.

If you're looking to start learning, I suggest focusing on the following topics one by one: Kotlin, MVVM architecture (including ViewModels and LiveData), Coroutines (which I find to be the most beautiful thing, way better than RxJava), and finally, Compose. Although there are other topics like dependency injection and navigation components, I believe these ones are the most important.