Coming from someone that just picked up the game over a week ago and playing in my first shooter game ever I would suggest three things.

First off, take every single fight that you can. Giving yourself as many opportunities as possible to run in and get experience in fights will help you get a better feel for the pace of the game. Going into playing KOTK I made that my goal no matter how potato my aim was. Only way you get better is practice and repetitions.

Second thing I would recommend is film your games. Whether you record them or stream them with a program like OBS Studio, going back and watching how the fights played out can really help figure out what your problem was for any particular fight. In my case scenario, I stream my games and a lot of the time I will have viewers in the channel clip my kills and deaths to go back and watch them afterwards.

Finally, after going back and watching the kills, if you are finding most of your shots are wide of your target, (left or right) I would recommend turning your dpi or in game sensitivity down. Anytime I have found myself in a situation where I am repeatedly missing kills on shots going wide I've turned my sensitivity down to help slow down and pace my shots.

I can tell you first hand this has helped me tremendously get better playing this game in a short amount of time. Goodluck dude!

 

Fearthebuns really said the most important already, one thing I'd like to add though. I'm new myself and about to reach 200 hours in the game now.


It may seem like a stupid answer, but what helped me a lot (and can be fun if you like it) is watching streamers. Watch how they play, how/when they fight, how they aim, how they deal with the recoil etc. etc.

Some I can recommend, I learned a lot from them myself:

Pineaqples
StormenTV
Ninja
OPScT

They're all skilled players, some of them are rather quiet (StormenTV & Pine), Ninja and OPScT do a bit more for the "show", should you prefer that.

Good luck, it's an amazing game, I'm having a blast so far!