object kind of transparent I'm not sure what is the problem, I downloaded few objects and some of them behave strange.
I mean that the object can be seen but in kind of transperent way. For example here the table surface should be clean.

but instead we can see the beams that under the table. I have tried to change the transparency but it's not the issue (if I understood it right). Any explanation what is it?
Edit:
I have tried to recalculate the normals, but it's not really works.
But I found that the object looks strange in the edit mode. maybe it's useful to  understand the issue.
I'm not sure if this will help but if you go into object mode and click on the overlays dropdown and say check the checkbox that says face orientation is the mesh red or blue? if any of it is red you can go into edit mode and select the parts that are red and press alt N to flip the normals. Hope this helps.