Hello. When i select a piece, i can’t click on “eclater”, the french word for the invers of “make a group”.
So i have a group and i can’t make the group disappear to stuck the piece to another piece , for making a new group.
see here : http://hpics.li/5b1f1d2
The reverse of making a group would be Explode in English. In your screen shot, you have the group open for editing and you’ve selected the geometry. There is evidently no group in the selection to explode. If you want to explode the group you show opened, close it first and then right click on it and you should find “Eclater” available to use.