Shading issues with spline meshes

Hey guys, I’m creating a modern city with UE & Blender. I thought spline meshes would be the best tool to create streets with (to save space), but when I added “buildings” which create shadows, the shadows look very weird and unrealistic.
I tried to solve the problem myself by making sure the UVs and lighting meshes are good, but it didn’t help.
Any suggestions?

The buildings are 2 separate static meshes.