I have the physical copy in spanish but i'd like to have the GOG version..
Please, add the spanish version.

You can just purchase the GOG version, then copy the Spanish language pack files to the GOG version (making sure you back up the originals!). It should work normally, but it might require a new Spanish language pack in case there's any changes (from my observations in installing the Widescreen patch, there isn't)

I do not know what the files are.