Thanks for the tip with ArtForm (3.5).
In my version I cannot import *.3dm, only IGES.
Connot finde in "Curve Edit" the way to /Modify/Modify Point on Curve.
And I had to learn more about working with ArtForm, so I cannot edit points from the curve now.
Thank`s for your help.
I see, it ist really possible with these "sidestep" to ArtForm, to change the curve form with curve points and reimport to moi very quick!