Hey 
I’m trying to bild a flat World with low poly Houses, trees,… and on one of my buildings is a Mesh Collider but if i try to drive against it (to test it) i just drive right true it. I tried to have a different Collider (Box Collider) but when i tried it it just lags my car in a different position, rotation. What’s the Problem?
Box, sphere, and capsule colliders are quickest to calculate and stable to work with.
With mesh colliders you can check is convex to make it convex. This is better for performance and more stable. If it’s concave (not convex), rigidbodies which are not set to continues can clip through.
If it works without mesh collider (maybe with multiple basic colliders), don’t use mesh colliders