Aspire - Open contour

Hello;

I am a newbie with Aspire and I need to cut the countour of my shape:

But as you can see it is sliced with multiple lines and it always complain about the open contours. Basically it say that if I want to cut in a simple contour I need to join it first with the countour tool. (sorry the screenshot is in french)


So for the moment it is doing something like this but I don't want the inside cuts.

When I try to join two contours it is doing some crapy stuffs like :


I have also tries to edit the nodes but is already looks joined:


Do you have an idea for me please?

REgards,

 

Well except if I missed something in the video, it didn't explain how to do the extenral cut but he explain how to vcarve on the open vector it isn't what I need to do?
But still thank you for the begin of response