Hello,
thank you for taking the time.
I would like to know how to solve the problem that a GameObject with rigidbody component sinks into a terrain.
I have attached a video 
where you can see my problem.
To move the GameObject I used rigidbody.movePosition()
Of course, I added the colliders to both objects.
Many greetings!
I think the move position method, moves the rigidbody ignoring colliders, you should move the character with a force… https://docs.unity3d.com/ScriptReference/Rigidbody.AddForce.html and using impulse as the force mode https://docs.unity3d.com/ScriptReference/ForceMode.Impulse.html
also don’t forget to lock Y position to avoid player falling to the ground