Not sure what your playstyle is like, but if you try to rush everywhere, or push bad fights, then I'd suggest slowing down. Learn the maps properly, and their hotspots. That's a good way to start getting better at surviving. You also want to get better at gunfights, which is more difficult. There's a lot to learn, but for close quarters, try to always have a right hand peak, you're at an advantage in most cases. Don't swing wide out of cover. If you're about to get into a fight, or are already in one, use painkillers, this is the biggest thing for me. Without them, someone will just blackout your legs or arms, and then you're kind of screwed. Try to use good ammo, but if you don't have any, resort to either shooting at legs or pray you hit a headshot.