Is it posibel?
Make the landscape hovering? If yea what is neded to do this? I dont have access to the code
Do you mean a floating piece of landscape geometry? I am sure you can do that… if you mean “can you get underneath an existing terrain,” I would have to defer to someone with more UE4 experience.
As far as I know it’s currently not possible to do that “out of the box” -> either use meshes + blueprints or somehow modify the code 
The only think i could imagine out of the box is use a normal landscape and fill with meshes the “under ground” or the “under side” of it.
But it could be very tricky to make it look good. And i don’t know if it need to have movement. In that case I think you can’t out of the box.