Get better in Call of Duty Black Ops 3?

I've been playing since black ops 3 the game has been out there, but I generally have a problem in every CoD: I'm not good and mostly stand negative. I don't understand why that is. I started playing the game on Xbox One for the first time and later (for a few months) on Playstation 4. Unfortunately, I'm only negative, I have more deaths than kills and I really don't like that anymore. I just play the game and still stand negative. It often happens that I'm 3 to 16. I usually don't feel like playing anymore, even though I give everything. Can someone help me there? Would be really nice.

I play pretty offensively, my aim is not that good and my movement above all is catastrophic

Therefore wait and proceed slowly. If your aim sucks, what do you hope for offensive play? If there's an opponent in front of you, you won't hit, but the opponent does.

That's why you have to trick your opponent differently.