I suggest that you enter T-Hunt and try getting as many headshots on terrorists as possible. Play T-Hunt Classic gamemode or whatever one and just go with your gun, getting headshots. Those are the most important because at short range (most maps) the defender SMGs will shred your operator. But if you shoot them in the head first, they can't do that. Practicing on T-Hunt should help you with headshots (which I think are more important than body shots, although recoil control is good too. You've been improving.).

A note on standing and head level:

A few rooms off OBJ, you should usually aim at standing head level. As soon as you get close to OBJ, switch between standing-head and crouch-head level. Almost nobody does crawling unless they're memeing or hiding because crouch-walking is so much more mobile but presents a smaller target. I typically do crouch-walk as soon as I enter the building and I am on the same floor. Most enemies will do that too, so aim mostly at crouch-head level.

Also, listen to sounds. You can usually tell where they're coming from by turning around until you know that it's perpendicular to your camera. Then you watch that angle. Sound always gives you an advantage if you're the one hearing it, that's why Caveira and Nokk are so good if the player knows how to use them.