ok this may look like a lazy ass beginner crying out for spoon feeding( which it kinda is), but i want some real industrial training in non documented Android coding.

For last 2 years i have been reading tons of Android articles and documentation on "how to use this library", "how to add this feature", "what this function of this class does", but not much about how to use it efficiently, like the way its used in industry.

When I interned with a startup, all they wanted from me was to push new design changes, fix layout bugs and work as fastly as i could. I had no time to understand their core code, which had so many things that i could have learned : those mvp/mvvm design/architecture patterns, dependency injections, kotlin , coroutines, state management designs, data bindings, eventbuses and handling, and VIPER,RIBS (I mean, not everything was particularly in their code, i picked up a few keywords from here n there)... a lot of stuff that is used by many apps for their codebase.
I can read up these stuff by myself, but i always end up feeling bored coz frankly, i got no big/valuable project to implement it upon and feel excited about it. I feel that open source projects from OSS companies could be my window, but their chat spaces are also mostly empty to discuss/get some guidance.

I want some specific training about these. Can you guys provide any online/offline course/company training/books in this subject, the best practices?

Great practice/skill sharpening idea for my fellow mad dogs that like to get down in multiple languages/syntaxes:

Pick something simple that won't cause too much stress, but will make you sweat a little bit and put up a good fight, ha!!!

For example, I picked the classic "Caesars Cipher" and picked 5 languages to create it in! I picked Dart, Java, Python, CPP, and C. Each version does the same thing:
1. Asks for a message
2. Runs the logic
3. Prints the message cipher.
4. To decrypt, you just run the same program again and enter the cipher text at the message input prompt. The message gets deciphered using the same logic an shows up as the original text.

The kicker:
Only dox/books allowed for reference. Otherwise it wouldn't push you to get better!!!

Python, C, and CPP were EASY, even with me never having used C before. I am great at using Dart, and that one really challenged me for some reason, but I finally got it. The previous 3 langs took less than 40 lines of code each (with Python being only 18 I believe). Dart actually took somewhere around 50, and Java took about 371784784. (Much love to Java though for real!)

Kinda boring as shit, but I gotta tell you it felt fuckin GREAT to look at all 5 of those programs after completing them, no matter how barbaric... especially when you complete 1 or 2 in a language you've never used or maybe felt really challenged by. Simple exercises that hold a lot of important, relatable logic no matter the subject is our lifeblood!!!