Yesterday, when I tried playing Titan Quest, it said my files were corrupted. Gog was down because of an outage in Poland, but when I tried loading Titan Quest some time later, I could play, so that was great. When I was unable to, it said something about not being able to update a channel or something. Weirdly enough, Titan Quest is the ONLY one of my GOG-games that doesnt say "save successfully stored on Cloud", my other games work too.

I had a reverse thing happen to me some years back when I was playing Path of Exile on a competing site, my PC broke down, but my files were saved on some cloud of some sort.

Can I do something to back up my saves? I dont see them anywhere in the folder.

You can try switching over to local saving. Back up the files on the cloud first, just in case. Then turn off cloud saving in the options menu/Galaxy if using that. Start the game up again which should trigger it to make a new SaveData folder in My Documents\My Games\Titan Quest Immortal Throne\ Then move the backed up files into that new SaveData folder. I think that will work.