Imported a model as FBX from C4D but it looks weird

I don’t really know how to explain it in words…
So here’s a gif showing my issue:

Why am I able to see through my house but it’s solid? The cutout in the door was made by Bool.

probably 1 sided mesh (example: unity doesnt draw backside of a plane mesh)

in 3ds max can use Shell modifier to make mesh 2 sided, not sure about c4d…

I still don’t get it. In c4d it is solid, meaning, I can see the wall through the door.

oh i see, initially its partly visible, then inside its not.

can you show wireframe view of the building?

Yup. Here you go:

Also, my window looks like this in the unity scene…:

But this is how it looks like in C4d:

Here’s the link to the house in both c4d and fbx formats (in case you want to have a look): Dropbox

*ok got the model

5326557--536271--upload_2019-12-31_13-54-13.png

That’s the window.

so the black part (that looks like wall) is actually door,

can see in the gif the door handle,
5326590--536295--upload_2019-12-31_14-7-54.png

but the main issue with back wall and window frames is still the one sided mesh.

If you enable backface culling (keyboard shortcut toggle N~P) you can see how it will look in unity.

My recommendation is also to work with your viewport → Options → Polygon Normals enabled, that way you can make sure your normals are facing outward