Questions about Cleaning up an .obj mesh

Please see the attached image. Thanks.

you can flip or recalculate the normals in edit mode via the [alt-N] = normals menu.
To visualize the face orientation there are some nice overlays, like “Face Orienttion”.
The cyan colored edges are marked as sharp (probably because the faces there flat in the original obj). There is a “clear Sharp” operation in the edge menu to clear it.