Will GoG Add the German version pls? :o

Seems they wont. There is Redump PC set - B colection and separate releases on Internet Archive or somewhere else. For PC EN-NA, EN-UK/EU, FR, GER and JPN official disc releases. You no need instalation i assume. You can take some files from KAIN folder on CD.

(There is also PS PAL Redump set for official localisation for Sony PlayStation (One) for same languages. Plus PS NTSC set for North America ENG 1.0 release and - what make PS platform special for subj game - few game pre-production beta's/unique demos. Redump set has just few, a bit more as separate releases on Internet Archive or the hidden palace)

Or just download KainGL Wrapper-mod. It have official FR/GER/JPN voice dub as well as some unofficial (rus) and texts. Including unique subtitles feature.
Unfortunately there is no more official public dl-links, googleit some mirrors.
There is mirror of official dl-link on Internet Archive — Web but "Download" lead to much older version than latest one, same for any you can find on google (no latest build) but still more updated than Internet Web Archive.

There is also fan-made remake Blood Omnicide, which as an engine almost completed actually. But as bunch of levels and very few items content it is unfinished and abandoned (no way team can do it further, there is many objective and subjective reasons, now incl war). Hypothetical anyone can grab latest official version, some sources and tech specs from their site+wiki and convert original level files into it. As an engine and source it is pretty much finished.
It has subtitles feature for in-game dialogues too. Both KainGL and Blood Omnicide make localisations easier (port of old ones or make new) and easier to switch languages.