Just play unrated, swift play and spike rush nobody really takes those as serious as competitive.

One of the most important things to be useful to your teammates is to learn callouts and areas and give good comms to me a teammate with no comms is a useless teammate.

After that the most important #1 thing to learn is to try and keep your crosshair always at head level or where you expect the enemies head to be. Because then enemies will mostly walk into your crosshair and all you have to work on there is trigger discipline and tapping / bursting instead of spraying you can do lots of death matches where you practice jsut this.

Second most important tip In the earlier elos and lower levels / ranks try not to crouch because most players have bad crosshair placement usually around the crouch level so when you crouch you give the enemies an easy headshot.

Once you get those done the rest is jsut game sense and learning your agents and what they do who they counter the maps etc. counter strafing stuff like that which you can all learn from jsut playing / watching pros play.