How to get used to the game? Tips for the beginner (Tom Clancy's Rainbow Six: Siege)

Dear soldiers of the Rainbow unit so I bought this game 3 days ago and I have something wrong. I've been playing shooters for a long time, starting with the CoD series and ending with the CS series. Rainbow causes strange feelings, there is no such openness and clarity in CS GO, for example: in CS GO round begins and you're running just to kill, but when I play Rainbow there is something not clear starts every mess, and the fact that every bullet can kill you, do not know where to go, what to do, kills 0. I don't know I need advice, maybe I'm too used to CS: GO and the atmosphere of the Rainbow baffles me. How to get used to it how to start making kills. I would be very grateful for any advice. I hope you understand me, and I'm not a noob I have Silver Elite Rank in CS GO 10 within 3-4 weeks of the game, and not constantly playing. Without cheating, I'm not that low. Thanks in advance!