Unsolved Model issue

Hi, I'm trying to make a bridge and in BeamNG it doesn't render properly and the textures aren't loading even though it generated a main.materials.json file.

Here is what it looks like in Blender

 

Im not certain on situations on this but if i had to guess it would probably be because the panes you made it with can only have a material assigned to them on one side.
Im probably wrong but i have no idea what else it could be

 

I remade the bridge and now the textures are working but only showing on one side and on the deck the road is only visible if I got underneath it and when I put a car on it falls to the bottom of the deck and eats the car. Can you or someone on this forum that you know solve my issue?

 

How can that be possible? It loads fine in Blender.

 

Idk much else about it

 

So, does anyone know a solution? I have made other objects in Blender for BeamNG and it worked fine. I'm going to make a map that has an Australian-themed highway with plenty of interchanges.
Here is a new bridge that I made that only shows the material on one side.

 

In blender, select all and press shift+n, it will recalculate the normals to the outside. you can click on the button with the two circles overlaping int the top right of the viewport and check face orientation, if it's blue it'll be visible, if it's red it's on the wrong side.