"Not your GPU because all other games run fine" is, unfortunately, not as good an explanation as it sounds. This isn't any other game; this is close to, if not uniquely, the hardest game on the market for any GPU to run.

What GPU are you running? This looks like problems I see when I try to run the game on a GPU that is definitely inadequate. ›››

the best thing to do is completely reinstall the game and when it asks you to keep your saves click yes. Also before you do that back up your save files from my documents/witcher 2 <-- back up gamesaves files then uninstall the witcher 2 and then reinstall it. once you've reinstalled the game update it to the newest version 3.2. then just drag and drop your gamesaves into the new witcher 2 folder created in my documents ›››