How can I follow the terrain

there is a huge difference between a slope and rugged terrain with smaller holes than the object we are talking about. Both can be seen as bumpy. It can help a lot if some things can be excluded from the equation.

either way: Can you at least describe what you mean be "there are problems"? what kind of problems? what did you expect to happen? what did not work? where exactly is your current solution not sufficient? Also have you tried using colliders or did you just go for raycasts?