ussnorway: if you got the bin files from Gog then that is a backup installer and they come in two basic types
1 Galaxy [extras] or
2 Browser
[see the images i posted as example]
the only difference between these two options is the size of the downloads, Galaxy gives it to you as one big 100G + file and browser breaks them up into 4G chunks but they unpack to the same thing on your Mac/ PC
you can only install off line patches onto an off line copy of the game so even if you used Galaxy to download the 120G copy it will not install over an older build of the game from Galaxy i.e, off line is one thing and Galaxy is another
1st step = look at my Galaxy / browser images and check if your file number is the same ending in 4900808 because if your copy says anything else on those main builds then its worthless now and you need to update
next step is 'show folder' & 'path' [see images]
what we need to know is where the current build of BG3 is installed on your system?
so if its in c program files then this is a Windows error and you need to pick a different location
but if its installed on an external drive like a USB stick or harddrive in a caddy this this is a user error and you need to make/ find internal space to put your game
no i installed using galaxy, but galaxy has been failing to update the game for like, ever now i dunno it's been months at this point i think. so i didn;t grab the install file from gog i grabbed the patch files from the same place you grab the gog offline install files.