Wow, after several years, people still have exact same problems downloading games through a GOG client! Amazing. And I thought Origins was bad!

Can somebody help me out of this issue. I was downloading Witcher 3 and DLCs on GOG Galaxy (using it for the first time), and started to notice that the estimates were getting stuck and becoming inaccurate. Then it got stuck at the magic number, 92%. Then I exited Galaxy multiple times, restarted the computer... Nothing. Then I dumbly aborted the download. Turns out it's back at 2%, even though +35 GB are on my computer now. More than the 35 GB it said it needed. What do I do?

Ok, now I've used the import file feature on Galaxy to make the game show up as installed. HOWEVER, when I turned off the computer and got on later, the game no longer shows up as installed. Great. Will I have to do this every time I play Witcher? 25 GB of updates need to be installed before it is playable, so waiting on that.