---

I checked more closely - I took a wrong turn in Hoverfly key (Bothe) there (I went one step in the key to far), but got it right now.
but found a key for the proxima-group in the web -
It looks like it is a Cheilosia cf. velutina -
even found the area of black bristly-hairs on tergit 3!

Thank you for the help