Just the moment I find the sarcofagus, protected by this couple of guys, Chang brothers, after script ends they should talk to me, that's what happens in a gameplay I watched, but they do not, and I cannot do anything, I can't move, use power nor attack.
If I reload, the same problems happens, even if I reload the entire level.

Open the console and type "camera_kill". Or does the game zoom in on one of them but he does not talk?

No, the camera keep on my character, I can move the camera around him, but nothing else.
camera_kill did nothing, and most the times I open the console, I can do nothing after close it.

If the console freezes, type "chareditor" and continue from there. As for the stuck player, type "frenzyplayer" and see if this works...

Nope. I was about to press F10 to get a screenshot, but I pressed F9, 'save' by mistake. It said 'cannot save while paralyzed'

I do have exactly the same problem, already tried to fix it with camera_kill as well as frenzyplayer but nothing happens. Still cant move.

I'm not absolutely sure but I have the feeling that there are multiple of those two guys standing "in each other", Possible that there are spawned twice and case a bug trough that?

What patch version are you using? Also ave you moved into that map and then up into the previous one before talking to the Changs? If you did, reload from an earlier save and don't do this...

I only have installed the latest version from GOG no further patches and no I din't went back into an other room.

To be sure I tried to load an old save game from before I entered the "Giovanni area" but that hasn't helped ether.

Hm, what version does it say on the gameplay options menu?

Menu says 9.7 Basic.

Did you continue an older save after you or GOG updated the patch to 9.7?

Never have played an other version, so no. Started the game with 9.7.

If there is no other way, is it possible to just skip the quest or similar?

Can you open the console and check for Python errors there? Then I might be able to give you a code to continue...

This is everything written into the console from the moment before getting the loading screen until the one where I'm stuck: https://gist.githubusercontent.com/mfxbe/15b94cc5bd5165829d57ceb17bb4ed3f/raw/30778d45b2841e327c72649fabab19bbdebd3fd0/gistfile1.txt

Uh, this looks as if the whole Python part of the patch isn't active. Did you switch between the vanilla and patch shortcuts during the game? Where is your save game located, in the Vampire/save subfolder or the Unofficial_Patch/save folder (I hope you didn't copy it from one to the other)? Have you installed a newer Python version on your computer recently? Do you get the same kind of errors if you start a new game? What is the date/time stamp of Unofficial_Patch/Python/vamputil.py and vamputil.pyc? Try moving vamputil.pyc elsewhere which will have it rebuild. Does this help?