I don't think I'm a great player but thought I'd give you some tips I picked up on which helped improved my game so much
1/ go to firing range. grab an r99. no barrell, no scope, no attachments. Try one clipping the dummy whilst stood still, you should be able to if you get a decent amount of headshots. next, try one clipping it strafing left to right. next, stand on the far right side dummy, then do the same for middle one, then for far one on left. its practically impossible to one clip the dummy far left with no ext mag unless you're nuts, but you should do 100+ damage
2/ if you see 3 people on your screen, run. don't even try to shoot. if 3 people shoot at you, no matter how bad they are, you are dead. tired of seeing randoms not disengaging, just run and reposition
3/ if you are in a 1 v 1, for the love of god, don't jump whilst you shoot. this isn't fortnite, and it makes you so much easier to hit. do the ADAD etc strafe and throw in some crouches
4/ heal before you loot, the loot isn't going nowhere. I see lots of people stood over a deathbox looting, not even shield swapping. you can't loot whilst you are dead
5/ if you play with randoms, play for YOUR LIFE, chances are, they are garbage and running to help them in a **** position will get you killed. they made that choice, don't make the same one they did. This one sounds really harsh but as someone who used to que solo, I know all about the calibre of randoms ( remember most of the player base is below average and the good/really good players usually squad up )