I've just bought the game and can't save nothing, not even the game settings as it resets everytime I close the game. I'm pretty much clueless about what to do, I can't even find a save folder in the game files. Please be so kind to help me. (I know this is'nt the proper forum but this one is way more active than the one specific for witcher 2)

Uninstall, then install in a non-Windows location (NOT program files). If Galaxy, go to Settings and change the game installation path before installing again.

Save games are probably somewhere in My Documents.

PC Gaming Wiki has you covered for save locations:
https://pcgamingwiki.com/wiki/The_Witcher_2:_Assassins_of_Kings#Save_game_data_location

I agree with the above poster though, it's most likely a permissions issue due to where the game is installed. On Windows 8.1 and later, it's best to keep your programs out of the system folders. Something like C:\GOG Galaxy (or C:\GOG Games if you don't use Galaxy) works well.