If you think sensitivity is going to help in a situation like that, then thats one of the big issues.
There is no magical sensitivity, and changing it is only going to make things worse. Pick one. Thats it. Learn it.
I wont specifically mention a setting to avoid confusion and generalizations, but you need to pick one that allows you to turn around at least once per mouse slide side to side, but lets you pick points on screen easily without over-correcting.
Ignore any mention of "x DPI makes you better", ignore super high or super low settings, they are gimmicky and people have made them overrated.
Make a custom game, set up some walls quite a bit away. If you cant predictably land on the middle of those walls with ease, practice that, learn your settings, dont change them around without commitment.
There also could be many, many more issues here. Latency, framerate, desync, etc.
Just out of curiosity, what do you play on? Have you played any other games without issue?