Whenever i try to install it it says
"Installer files missing- please make sure you have downloaded all the parts. You will be asked for their location during installation. Intergrity check will be skipped"

I've installed both parts of the installer, the .EXE and the .Bin folder.
as well as the universal update.

Yet i cant install the game when i locate to the .Bin folder manually, because it gives me the message "Installation cannot proceed without the required file" and i can't open the .Bin folder because it's locked and i don't know the code.
I've tried downloading both the .EXE and the .Bin folder multiple times, but the outcome is always the same.

Anyone know how to fix this ?

You need to download both the .exe and the .bin files and place them under the same folder (for example, Downloads\GOG Downloads\Heretic Kingdoms), then run ONLY the .exe file. There's no need to mess with the .bin whatsoever, you don't need to mount it, extract anything from it, nothing, all you need to do is leave it inside the same folder where you've placed the .exe file. I'd reccommend running the .exe as administrator.

If this still fails, make sure to delete the files and download them again.

It worked, thanks so much :)