Imported Model with Generated Colliders (Convex) problems

I created a simple Moving hill (posted below) that has a gap in the middle that the character must run through.

When I generate colliders in unity, the collisions are fine but the character goes through the object. When I try to click the convex box, it creates the colliders but I am no longer able to pass through the gap. It acts as one solid hill without the opening in the middle.

I read somewhere that movable scenery/objects require a collider and a rigid body.

So I tried adding a rigid body with and without convex applied but it did not work as needed. I also realized that rigid bodies on non-convex objects are no longer supported in unity.

I know that one solution would be to create my own colliders by adding primitive shape colliders within unity but I feel this would not be helpful since I would want a smooth hill rather than cube colliders positioned together to imitate the hill.

I heard there was assets on the store that would do this for me, but would rather figure this out rather than take the shortcut.

Any assistance would be appreciated