You will see that if you click on lines in 3D that there are both CAD Polylines and CAD Lines in most locations - The CAD Lines are what you want - the CAD Polylines are the Closed polygons and they are useless for anything other than snapping points - but the CAD Lines are only following the Top of Surface elements and you can use those to form models from. You should relayer the Circles and CAD Polylines (use Advanced Select to eliminate them from your "Usable Data:
These are on C-Markers Standard and C-Shapes_Border Line
You can make surfaces out of these lines, however because there are nodes vertically above and below each other you will get some Flags on some elements - Use Trim / Extend Lines and Trim the lines that are problematic by Distance say 2 or 3mm to eliminate the vertical faces - it is time consuming - you could also draw a longitudinal line between nodes and then offset by a mm etc as an alternative approach to the same issue - same for Vertical Lines - if you need to trim them back you can either use Break and Delete or you can Trim them by a distance and that will shorten them
If you add all the "Section Data" for each Surface into a Surface Model, and then add the Road Alignment to it, you can change the Surface Properties ti Alignment Based and then you can apply the Densification to it in Properties also to densify the data through the curves (Hz and Vt) to build a better surface from the data provided - I would just do the Top and Bottom Surfaces most likely and If I needed the Material Layers then I would add those surfaces as Surface Instructions to a Corridor Model and then I would most likely build the Subgrades using the Corridor Modeling Tools but coming off the Surface Instructions / intersecting with the surface instructions.
You also have to ask yourself is the Data Prep Process from the CAD file going to be quicker than building a Corridor Model from Scratch - these types of road are typically pretty simple and don't have a lot of cross slope variations
Here is a video of how I would tackle this
Hope this helps
Alan