[2021] Planning to come back, anything I got to know? And should I?

Welcome back! My recommendation is to watch the Waterline videos to have some idea of recent and upcoming changes.

https://worldofwarships.com/en/news/general-news/waterline-what-will-happen-next-4/

Also a good idea to read about the recent changes to submarines as they have had some changes from the few first tests that you might have seen before you left. Yes, I agree with @Nevermore135 that the re-work is something you want to check out.