"Plain" 3d arc/circles imported from DWG/DXF are recognized as such in the SKP, so you can then change their segmentation in Entity Info later [there is also a script to change selected arc/circle's segmentation en mas sin the same way]. If the arc is part of a 3d form it's not changeable.

Thanks for the information. Yes indeed in the file menu i can import dxf and dwg files but i have still a problem left. When i for example draw a circle in autocad, save it and then import it in sketchup (even when i have already a component in the scene)the circle apears in the scene but there is no surface created such as when you draw a circle in SU. My intention was to draw complex sections in autocad and then export them to SU to make 3D models of it with for example the push/pull function.

Align Tools 3D by Didier Bur Component onto face by Chris Fullmer

Look in the 'Tools' menu for 'Angular dimension'... Not every loaded script shows an entry under the 'Plugins' menu... You can often find in which menu a tool will appear by opening its .rb file in a plain text-editor [like Notepad.exe] and looking for the menu code, which is usually near the end of the text - it's usually clear where it shows and what it's called... That's what I just did to tell you where to look...