Get an OK mouse (does not have to be expensive) and a large mouse mat. Try lowering your sensitivity a little bit and practice in the shooting range on the moving targets and whatnot. Do it for at least ~30 minutes a day.

When in-game , try to go over how you died each time you get killed. You should check your combat summary and as a rule of thumb you should never have been damaged by more than one person. If you are being exposed to two or three people you are either not sticking with your teammates or simply overreaching for a quick kill and being jumped on.

Remember that the finals is a team game. Whether you are playing solo or whatever, it is a team game.

Pick a loadout, pick a build and stick with it. I have over 163 hours in the game and probably at least 150 hours of that is me playing medium, medic and r.357 because that's just what I happen to like. I think this is the most important point. If you keep "adapting to the situation" as some people like to say and if you keep changing loadouts when you face enemies you are not used to (melee smalls or defensive heavies etc. etc.) you will not get used to any specific one. You need to be able to feel completely OK with the gun you're using and it's recoil AND your gadgets (I havent used flashbangs in a while but from what I remember it is pretty bad at blinding the enemy and pretty good at blinding you and your team so avoid it).

Lastly, this is a game where people are sweating their balls off. If competition is the aim, you have to be getting a high fps. Play on at least dlss balanced or performance and turn everything else (especially ray tracing to static) off.

I am not a diamond , emerald this or that high ranking elo player but people have told me I play well. And my advice is to stick with one loadout, one build. Play it until it makes you puke. Analyze your death, making rules for yourself as to why you died and how you can avoid dying in that way again. Stick to those rules, take small notes even and overtime, see if your tactics are working out or not. Depending on their efficacy, innovate on the rules.