Black Artefacts before AND after Export

Hi there,
at first: My english is not the best so i hope you can understand me and my problem.

Iam desperate because i dont know how to solve this Problem:
While editing via via timeline, everything looks good (no artefacts, no problemes), but in that moment when i want to export the video, the quality is changing. I have tried several settings (change bitrate and other settings etc) but still the same issue: Black artefacts ("brocken picture") on the edges.
First i tought that it will change after the video is renderd but i was wrong...looks bad as the preview (render window).

Hope that somebody can help me 😕😕
Thank you & be safe

PS: depending on your monitor settings you can move your head from left to right / right to left to see the artefacts i was talking about