From four out of five attempts the briefing video have kept freezing, only the text have changed. And at the first try I saw only a black screen. My specs are way above the system requirements. This is nonsense, I am seriously considering refunding this game. :(

I had the same problem, just use esc to abort the briefing and the prolouge will start normally.
Aside from this i had no technical problems with Atom.

Hello!
Sound's like a bug. Please, can you send us your log (%AppData%/../LocalLow/AtomTeam/Atom).
Also, please send us the dxdiag. In order to get it select Start and enter dxdiag into the search box on the taskbar. Select dxdiag from the results. In the tool, select Save All Information for an easily shared format.
Send both at support@atomrpg.com.
Sorry for the inconvenience. We will try to fix it ASAP.

Best regards,
Atom Team

I had a similar problem, but on the bright side you don't really learn anything crucial from the briefing video. In my case it was the only one which lagged, the few in-game cutscenes and the ending all worked fine.

Hello all

IDK if there´s any solution to the constant game freezing, but I think the solution is to disable GOG´s CLOUD SAVE SYNC, I just did that and I´m playing with no problem.