Learn the maps, bro. If you know the spawns and choke points, you got the upper hand. Turn down your sensitivity a bit, aim will feel way smoother. Trust.
Stick with one gun and get cracked with it. Switching too much messes you up.
Watch some Twitch or YouTube and copy their loadouts and playstyle. Works wonders.
And bro... stop sprinting around every corner. Chill and pre-aim more.