As for Mafia 3 to change the resolution

Changing resolution in Mafia 3 is quite easy. Just go to the graphics settings and find the right option.

The other, more complicated way is to go to the game directory and open the properties of .exe file. You’ll have to add "-windowed –noborder -h [height] -w [width]. Instead of “height” and “width” you need to type in the needed resolution. Then you can save changes and launch the game.