And when will gog galaxy be completed, it seems like it has been on beta forever

There was like literally a post right below this you could have asked about this... as far as an app, nobody knows.

https://www.gog.com/forum/general/when_will_galaxy_be_finished

Gog galaxy app, if one is made, will only be used for browsing and buying games, chatting with friends and browsing forum. And perhaps for additional security the way steam make use of it's app.

Judging from how forum is implemented and how galaxy is still has problems, we are not likely to see one in foreseeable future