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The first picture has already been posted 12 years ago. It is in the photo gallery as taken on 15.07.2011:

https://diptera.info/photogallery.php?photo_id=24

Anyway, Dasyhelea flavifrons (male) seems to be a very good guess. The species is estimated as 'not rare' in Germany - just underrecorded.

Greetings - Günter