Dear @Box
Thanks for your reply.
Inside of this part, there is like separation between the green cyrcle and cone.
I guess it would be better to separate it and continue my issue only with the cone (grey)
However, I do not know how I can separate this part in two part
Is possible to plit it without affecting my work?
In the green part, it’s easier to make a hole, but then I would need a “cylinder” in the cone part for a screw as you try nicely to help.
EDIT: I am jus trying to duplicate it twice and remove the bottom (green( form the first, and remove the top(grey) from the second duplicate