Hi sven, also you wrote:

> b) work in a flat plannar way only rounding a curve
> (I guess i apply the fillet to the base curve and that
> is not the good way)

Sounds like you may have some of your original construction curves still hanging around and getting in the way of selecting edges which are right in the same area.

Try hiding or deleting those original curves so that they won't interfere with the selection of those edges.

But that's a bit hard to know for sure just from a text description - if you were to post the 3DM model file where you ran into this problem, it would help a lot for me to be able to see exactly what you were running into.

- Michael