How to make flatten face to existing terrain?

Hello,
I would like to make left terrain same as right. The left one is completely flat. Is there any solution? I need to have these greens and parking lots leveled succesfully on the right object.



frm.skp (3.2 MB)

This video can help you… https://www.youtube.com/watch?v=dkJGPe3d1X0&t=14s



something like that