First of all thank you Michael for the way you showed me.
I had to reconstruct it and now I got two problems:
Altthoug the scipt of Frenchy tells me "noLostEdges at the filleting seams - I cannot do the fillet. Tried pretty much...where is my mistake?

And...I tried the workflow bending the geometry and it was ok. But now the geometry is at opposit site. Is there a simple way to bring it vice versa like at the screenshot sketched?