Hi Defonten,

> Thanks a lot Michael, but could you pls clear this untrimming process up a bit more for me? I try to
> get rid of those edges and they're just won't be deleted. What am I doing wrong?

You're probably selecting just one edge and hitting delete - instead you have to select an entire trimming boundary and then push delete. A quick way to select the entire boundary is to select one edge and then use Ctrl+A for select all.

If you have a version of this file with your original curves in them you used to boolean against you can just copy/paste that over instead of doing the untrim.

- Michael