When I open the file I see this:
I then deleted all texture nodes because there aren’t any textures in the file.
When you clear the custom split normals, all looks fine, except you get sharp lines where the angle between faces is larger then 30 degrees. (Setting Auto Smooth in the right panel)
When you set this value to 180 degrees, all edges are smooth. This is my prefered way to do this. It looks like you messed with the normals to get edges round looking where auto smooth at 30 degrees won’t make them smooth. If you want to have certain edges sharp, you can mark them sharp or put extra geometry around them.
And, sorry to say that, UV unwrap of the front seat is a mess. The back seats are way better. On the front seat the UVs are overlapping. So you should use Smart UV unwrap to get nicer UVs.