Hi, I have worked for several hours on a project and everything was ok. But the program stoped showing the preview video sometimes (some parts of the video) and it is geting worst until the all video is black, but the audio is always good.
Hi Reiner and welcome to the user to user forum for Magix Video Deluxe.
Your PC specifications may be very good but do not meet the complete specifications laid out in the Specification page for Movie Edit Pro (Video Deluxe) that states it needs an Intel GPU as well for complete compatibility.
You may find everything works fine if you turn off all Hardware acceleration options within the program settings.
Monitor refresh rates have no bearing on video editing that tops out at 60Hz.
If you are using this program to edit video gaming captured by a screen recording program you may encounter other problems as well if the screen recorder is set to record at variable frame rates.