When importing dwg or dxf files, all curves are lost
SketchUp represents curves as a series of short straight edges. If they are small enough, below SketchUp’s minimum edge length, they might not show at all.
What version of SketchUp are you really using? There is no “SketchUp for Web (Free only)” “2024 Desktop”. What operating system? “2024” is not an operating system.
One way to improve importing or translating of curves to segments is to break your larger curves in CAD up into smaller curves…so that they’ll each contain more segments. Not ideal if you have lots and lots of curves I know.
AutoCad also has a function that breaks spline curves into approximately correct polylines with arcs and straight segments.