Today makes 1 week of failed attemps of re-downloading cbp2077. I searched through reddit and GOG forums for hours and hours and tried so many advices and "solutions".
If someone have been through the same problem and managed to find a way out of this hole, please tell me, any help is appreciated.
Or if someone from GOG sees this, a refund so i can buy it at Steam would also work.

Have you tried downloading the offline installers through your library here on the gog.com website instead of downloading through Galaxy (which I assume you're having problems with)?

Had to re-download the whole thing a while back too (due to faulty patching by not temporarily removing any mods BEFORE applying the patch) and can confirm that there are no issues (re-)downloading the offline installers (provided that you have enough space and/or it's not anything like your internet connection dropping out, of course).
If the problem persists it might be something on your end.

thats the solution for your problem and you figured it out by yourself. i can highly recommend this way, by my years of experience on the customer-deathtrap called gog

I know ponczo states you should contact their support team and I definitely agree but here is a suggestion of my own based upon previous incidents similar to this:

Make sure you whitelist GOG Galaxy in your security software; be sure to include the executables in the Program Files folder, the AppData folder and others related to the client. Also, if you're using DEP or any other sort of software like Microsoft's EMET, ensure that Galaxy is fully whitelisted in those, too. When I was having download issues months ago, I discovered that my installation of EMET was blocking them because I was trying to force all applications to run DEP, SEHOP and other mitigation methods which were blocking the installation.

More recently, I had an issue like this and the only thing that fixed it for me was to fully uninstall and reinstall Galaxy, though obviously, that's a bit of a pain and probably should be one of the last things you try.