iMovie export problems

Hi everybody. I want to create a trailer in imovie. The issue is that I'm experiencing the same problem that a lot of imovie users are faced with: the export quality is very bad, especially for dark images. The preview in imovie is actually much better than the exported trailer.

My question is: has anybody solved this problem with different export settings for example? Or in a different way? Can anybody recommend me an alternative software to imovie and of course the very expensive final cut pro?

Thanks!