Can't seem to divide the selected face into separate faces

Im a upcoming 2nd year urban design student. I’m fairly new to sketchup, but know how to use the basics. I Imported a DWG file from AutoCad so i could make a 2D plan into 3D. Im having a lot of trouble with connecting the faces and lines.

The main problem I came across is a single face that I can’t seem to divide in different faces/parts. (In the picture u can see a selection. This selection is all a single face. I need to seperate the face
so i can push/pull certain parts. I’ve tried different functions and extensions, but nothing seems to work. The lines that border the face seem to not be connected or something.
can someone please help me, ive uploaded the file down below.

verkaveling sketchup.skp (1.0 MB)

There’s a lot of garbage geometry in your import that needs to be cleaned up. Zoom in close and look for overruns and duplicated edges. In my screen shot the cursort is near a gp at the corner of the shape showing the heavy profile edges. That gap needs to be closed. Plenty more places that need attention.

I drew in an edge to close the gap and you can see the edges of the shape are now not profile edges meaning the surface has been split there…

It would be a good idea to fix the incorrect tag usage in the model before you go much farther with it.
Screenshot - 8_19_2022 , 7_31_32 AM
ALL edges and faces should be untagged. Only groups and components should get tags.