Hi office, I have a couple of suggestions for you. First, I noticed when you brought up your Project Settings dialog that it was set to 805x719; that is an odd size. It *could* be an issue to encode to 719 instead of 720, and getting an even number (preferably a multiple of 4) for the width could help. Second, you could try using "Export to MainConcept (mp4)" instead of "Export to Mp4" (apologies if these terms are far off in the German translation). Third, the color: Red is notoriously bad to encode in MP4s, so you might have better luck with another color.
Try out a couple of things and remember that you can select just a portion of your video to export so you don't have to wait for the whole thing to encode just to test different options out.