"You can also quickly mute new alert and notification sounds by resting the palm of your hand on
the watch display and holding it there for at least three seconds."
Thank you. Well, I did unpair and reset the Watch to factory settings. By the way, the Watch itself has ambient light sensors and I didn't mention brigthness change in dark or bright places.
Is there an Apple Store where you live? Otherwise I'd contact Apple Care via phone because your watch might be defective if it even doesn't work after the factory reset..
It wasn't earlier but it is now. When I tried hard reset and than the cover to mute it crashes and reset. But only once. After that covering the display doesn't do anything. But If I make a hard reset the watch will crash and reset once again. Strange. So only software problem. I can live with that for now