This video explains what you did with the sway.

https://www.youtube.com/watch?v=aapuwsGglvQ

And this.

https://www.youtube.com/watch?v=rA4YyNPp0BM

I today launched Arma and here's the resolution of the game. I don't know why it changes itself, it's so annoying. The ifrst image is after I launched Arma 3 and the second one is from after I quit the game and reopened it. Also the languge has changed from polish to english and all my key bindings are gone. This is unacceptable. I spent so much time on rebinding the keys and now they are gone.

Hello.

"I want to report that the weapon sway in this game totaly ruins the game."

This is a MilSim if you think you have no weapon sway when looking into a scope on a target hundreds of meters away or right after you just stopped moving you are sorely mistaken.

"Another issue I have, out of hundreds on my list, is that sometimes the game opens in a ridiculously small resolution, everything is so big so I have to restart the game."

Updating drivers and checking if you have the correct resolution. Even reinstalling the game might not be a bad idea.

"Why did the guy in the above vide could have F2000, and I can't?"

You can actually. In the guerrilla camps and even other HUBs you can take a different weapon than your default loadout if you wish, just look around more. Plus you can take weapons from fallen enemies that is a feature of the game.