Twinmotion to UE5 VR template, Navmesh & datasmith collision

Hello everyone,
I can hardly find resources on working on a file from Twinmotion in UE5 using the VR template; so I have few things that make me confused;

  1. How to create collision to each element? Is there a way to apply to all? Or it should be done manually for each element?
  2. I have tried to add a Nav mesh bounds volume and made a collision to the same area where the Navmesh was, but I wasn’t able to teleport, I see the arc but it looks like it penetrates the ground (?) and I can’t teleport in this area.
  3. When I turned on the navigation (P), not the whole area where the nav mesh was green, why?
  4. I have irregular ground, not the same level and even in the same level, some parts are tilted, could that be the problem? And how to solve it?

Thank you.