Best games to work on fps type of skills (for PC)

Embarassed to say this, but for a long time I played games with god-mode because I loved the story or something like that, but wasn't good at action part.

Few years since I stopped doing that, but I'm struggling with getting better at shooters. Slower paced games, where I can take cover, time to aim, not pressured by anything are decently easy for me.

Main things I struggle:
- Aim with guns (a blind person would headshot faster, *unloads a whole clip into enemies cover*)

- Reflexes (sometimes I think I was born without them)

- Coordination (wtf is shooting at me, where is it, where am I, what is life)

Overall I struggle with faster paced (infinite mobs shooting from everywhere etc.) fps games.

Please recommend single-player action or fps games that you think would help me develop those skills, because honestly at the moment I suck so bad (non-horror ones).

I play co-op games with my partner and sad to say, he does most of the work. And playing co-op shooters hasn't really improved my skills, because what I don't kill, he will.

Thank you for reading and thank you for your answers.

You could always play Call of Duty with bots (squads) or increase the difficulty on the single player campaign as you get better.

At the end of the day it's all about practice, practice, practice.

You won't get any better playing coop. You need to play against real people who are better than you. Not sure which game is good for you, I know BF4 has a big player base which is a good thing, and it's only $10 on Origin.