How to make buildings so can't walk through??

I have some building and road models but my character goes right through them. I tried using mesh collider but it didn’t do anything… I probably don’t have it set up correct r need something else?

You’re probably adding the mesh collider but not adding the mesh to the component, check the mesh collider docs: Mesh Collider

if it does not work, try this:

Go to GameObject—Create empty

Then add a collider to the empty GameObject: go to Component---->Physics—>Box Collider

Then just drag your box into the building and re size it and make it the same size as the building,

Do what @Noah 1 said, but also check that both components do not have a mesh collider. Mesh colliders can not collider with other mech colliders. Make your buildings mesh colliders, and maybe your character as a capsule collider?