Actually my initial point 2 has been "forgotten" while point 1 has been resolved

1. 1) the software interface menus are very big [..]
2. 2) when i double click on a .sh3d file, sweethome 3D does not start. The archive software starts. doing "righ-click > open with > other application" lists all my application, but SH3D does not appear in that list.
   However, SH3D is installed and can be started via the applications menu
   [/list=1]. How can i resolve this?
   
   Many thanks in advance for your help,
   
   OS: Linux Elementary OS 6.1 (fork of Linux Ubuntu)

does someone have an idea on this issue?