Cull
Back Face! You've turned off all of the polygons that face outward, leaving only the internal structure.
Now that I see more details of the model, I think there might actually just be a scale problem. I'm not willing to say that for sure, but you have a
lot of polys very close together, and floating point numbers can get imprecise when they get very small or very large. In the two Merge3Ds right before the renderers, increase the Scale to 100. That will move all of the pieces further away from one another, allowing the renderers to more easily determine which polygon is supposed to be in front when they're very close together.
Culling the back face might still be necessary, but give it a try with and without it to see what happens.
You also asked for tips on getting a more realistic-looking render. First, once you get the forward-facing polys turned back on, you should see the texture properly, and that will help a lot. You may also want to give it a Reflect, particularly if you plan to show a bright object behind it with a low angle like that—as a surface becomes more parallel to the camera, its reflectance increases. Even very rough surfaces can become almost mirror-like at a shallow enough angle—that's what causes a mirage on asphalt.
Vito LaManna has some great tutorials on look dev and lighting in Fusion. His Patreon is definitely worth it.
https://www.con-fusion.net/home