hi, i was trying to install the witcher 3 with gog galaxy but every time i try it says server problem, any ideas?

try the gog downloader and links instead
https://www.gog.com/downloader

galaxy is still an alpha pretending be a ( barely functional ) beta

things tend to break

Galaxy works without problems for me. The only problem i encountered - it doesn't track time for Mount & Blade (original) and occasionally, gives error mentioning "virtual function" when i exit it. That's it.
I have 12 games installed at the moment.

I'm on XP though (and do not have Witcher 3). Maybe there are problems on Vista, 7, 8.1, 10.