Trim Mesh with Surface

[constantin.adomat]

Hello!
I have some problems trimming the mesh with a surface. Hopefully you can help me out in this case. Maybe its just a command which I don’t know.

I just need the Edges/Curves which are inside the surface. How do I do that?

[constantin.adomat]

I managed to solve it. But now the Boundary Surface doesn’t work…