Dimitar:
One option is to start with an Object, convert it to a Morph, then use the Morph
Modify Segmentation... > Fewer Segments command to reduce the number of polygons, then save the altered Morph as an Object for placing in the model. The converted object will not be parametric as the original, so set the parameters before conversion. If you go to Help >
ArchiCAD Downloads, you can get to the
Goodies download page, where you can download the
Polygon Counting Tool which will tell you how many polygons are in the Morph as you simplify it.
You should add a Signature to your Profile (click the Profile button near the top of this page) with your ArchiCAD version and operating system (see mine for an example) for more accurate help in this forum.
David