How do you fix an open polysurface/non manifold object?

I’ve tried to redo it, to convert it into a mesh, and use meshrepair, but it doesn’t work as epected, to selecte individual vertex, and if they do move without the rest of the geometry, to snap it to anothere vertex

here is the file:

Here’s a good start:

Hello - you need to remove the internal faces on this object to be able to close it.