So I bought a game from GOG and I installed GOG galaxy and everything was working good for 2 days, today I tried to open both and nothing works, it says it's already running on another account on this computer, im really now to this netside and I would like help, sorry for disturbing

Try restarting your computer, this happened to me a month ago and restarting fixed it.

You should still be able to run the games by using there EXE files in there game directories, make sure it is the EXE and not the shortcut file.

Do exactly like wolfsite wrote in the post above.
Many people don't seem to know that even games installed through Galaxy can be run offline through the executables in their installation folder.

Thank you for this, it worked