Correction,
C4D will import 2d elemants in a DXF, but not splines. Lines, circles, arcs are OK.
I only had experience exporting DXFs from autoCAD, and strangely enough the only way to get 2d objects in is to in “save as” go to tools and set “select objects manualy”, with automatic – no 2d comest through.
If you can import the dta into ArchiCAD, convert to to slabs or terrain and export as 3DS – works 100%
IQ