DWG > DGN ref. slowing down OpenRoads

Hi

I have recived a DWG ( Revit model converted to DWG) from an architect I work with. I have taken tis dwg and "merged " it in to a dgn to use as a reference.

I experienced my system to be extreme slow when working with this merged files... both directly or using them as a reference. Not the first when it comes Revit model / DWG.

Are there some guidelines when working with Revit models / DWG in a OpenRoads Designer environment?

Is it possible to "Clean" it up somehow?

regards

Sigfús