

Can you tell me which Nvidia card you have? Your comment “since a few weeks” makes me wonder, were all working fine before?
If your other games in GOG work then you could try disabling the Steam Runtime environment. In my computer I would be using Steamtinkerlaunch for that, so you could try it.





Might as well be, are you in an older Linux Mint version? Although if the Heroic games are running fine there shouldn’t be a problem.
Btw, if you run steam from the terminal you can probably see if there are some errors reported when running the game.
You might also try running your game through gamescope that might work even faster.