Please check out the news:
Perhaps there is a better way for you in the next release.
A few points after opening the file:
The scale is an estimate, based on the stove. If I open the file with Scale set to 1 and cm things get rather large and the apartment is rather super small. The Top Parent is too far away for anything to allow for a comfortable work. Since it is a visualization, the orientation should be comfortable as well.
The orientation and the large distance to the Parent Null gives me the idea that this is a “cut out” from a larger object. So, if that is a multi-angle object after all, you might find a different angle.
Pretty much no line creates a closed spline. So, no quick pick up and extrude.
Overlapping wall drawings indicate a CAD work-habit that would not allow for a precise material volume estimation, but I guess it was 2D and not 3D to begin with, so that is certainly no concern here anyway.
The windows are not sitting in a wall, they kind of draw the wall.
All of that leads me to:
If you ask me, the given data is more like blueprints that one places under transparent paper and starts “inking” from there.
In terms of C4D “inking” this would mean here, to take the Spline-Pen, set to Linear. Then trace by hand.
We have done this back in that days often, start from scratch and won awards anyway with the final visualization. It is nice to work natively, but yes, it is a time investment and that might be not really working if strong competition is given.
It seems to me that the source application is created only in 2D. One can’t make sections on different hight-levels for example with 2D data sets, which would otherwise allow for a wall plan without windows and doors, but if 2D is the only export option, that is the way you have to work.
I can’t shake the feeling that there must be more, there must be a better way. Here I can see no really advantage of the CAD material (expect snapping) over a blue print. Which results only to start over and use the given information as starting/snapping points. See the short screen capture. I keep them at one minute, so they are not seen as tutorial nor 1on1 stuff. I only compress the time here often, You can download these one minute clips of mine and stop at any point more easily.
The first thing that I did, was to switch off the Instances, as they seem to be given for all Null Parents in the file, and so doubling the information.
The scale was way off with a setting to 1 while being in cm. You have given no reference of how you want to have it, since I worked two decades in the metric system, I would prefer that of course. Anyway, the stove was used here as a standard
The scale to import was 100.
I replaced the parent with a localized parent, as you can see, I make it first a child of an element, to get the local position, then all of these elements will be child objects of it, while zeroing out the parent. Now using the H or s key to center things will work. Before, it was just ugly.
I have “traced” only the floor to keep it short, but once you get a hang of the perpendicular snapping/guides, you will be very fast. I work again here with a spline, but polygons (Pen Tool) can do the same: Selected polygons can be extruded, perhaps a faster way for you. However it is a artist decision what will work best.
Here is the screen capture:
My best wishes for your projects.