Blender is not NURBS modeler (even though it has a basic shapes) ...
Also I'm not sure if DAE can handle this kind of data. Export is usually converted to polygons.
To smooth curvature you can
- simply use Shade Smooth with Normals set to Auto to keep edges sharp ...
- or with combination of Subdivision Surface modifier limited to Angle ...
- or create an curve oval shape and use another curve with such vertical profile to be Bevel of first curve
Under blender 3 it can be done also via Bevel Profile properties of the first oval shape ... See Manual
