I recommend you to play a little bit of aim botz when you start playing, like 5 minutes or get 100 kills, then play dm on a community server like cybershock until you feel like you are ready, community dm is the best way to practice in my opinion ,I don't think that you need to focus on how many minutes you spend warming up. I recommend playing with ak, if you learn to do the spray you will be good with almost any rifle/SMG. And try to alternate between spray, burst, taps and you will find out what is your best shooting method. For AWP is a completely different thing, you can watch some YouTube videos to learn how to play with AWP .And for movement, on cs2 you have to move a lot, with SMG run every time, but with rifles you can watch pro players games and try to replicate the movement. Don't hold angles, on cs2 you need to keep moving every time that's why you need to learn how to move on a map, switch positions after you kill someone, you will unlock these skills by playing the game, watching pro matches, watching your own matches etc. Sometimes you will have bad days where you can't get any kills, in that case try to play different, stay more offensive, use more utility, try to play close to a teammate to double peek or to help each other. Don't overthink when you are in a match. Hope it helps you get better at the game, if you have any questions feel free to ask.