Importing pbx produces many meshes instead of one

I have pbx file with skelletal mesh and animation and it imports fine into uefn, everything works but the issue is that it has too many poligons. A million.

So I imported the file into Blender and reduced to 10%.

After long trial and error I finaly managed to get everything imported but it imports parts of the mesh separately and also animations separately and I do not want to manually arange all of that in ue. I want single mesh and single animation, just like it was the case with original large pbx

Any ideas on what I might be doing wrong here?