So there is this problem that if i alt tab out of the game and i go back to it the screen is black until i turn the game off. Also if i try to load any save if I die, the loading gets stuck forever. I installed Community Patch and the Update Pack. Windows 11

Try entering the game menu (ESC key) before alt-tabbing. If you use Galaxy, try disabling the overlay. Try installing the Parallel Universe Patch.
By the way, as far as I know, the Community Patch is already included in the GOG release, so double check if something went wrong when you installed it (again).

The problem is that even if i use a teleportation spell same thing happens. Any ideas?

I do not remember whether I have the same problem as the first one you mentioned, I stopped playing the game months ago, due to the second problem you mentioned , which occures to me as well ,and the fastest way to get unstuck is to press cntrl + Alt + Delete and choose to exit my Windows 11 Pro account ,and re - enter it. Also, I remember that months ago, when I abandonned the game for the above mentioned reason, I didn 't have any problem with the Teleportation Stones, but I 'm afraid to test it now because of what may happen.
About my problem which I mentioned I have, I tried EVERYTHING and NOTHING works. Uninstalling the game, re - installing it, installing its default patch (the game has the latest version of the unofficial patch installed by default), nothing works.
EDIT : I have no problem with Teleportation Stones. Also, except getting the Forever loading bug after I try to load a saved game, I get the black screen if I hit Escape and try to exit the game. I I use the Gaalxy 2.0.51 Beta version of the client.

Thanks, man, it looks like the parallel universe patch was the solution, if that 's the case, thank you!