Unity Platformer Problems

When I try to play the 3D Platform game, the firstPlatform object and the surrounding floating platforms bluntly fall and the Lerpz player falls through/disappears. Obviously this makes it impossible to play. As far as I know, I did nothing to the platform itself and I am merely at the step in the tutorial where you add Lerpz’s animation.
Can someone explain what’s going on?

You need to follow the tutorial step by step, I did this one day and works for me.

Well, anyway, the objects needs “Colliders” to prevent this.
And a rigibody to the Physics.

In the rigidbody you can set the “isKinematic” so that the object doesn’t move.

So, if you want to have to objects, a falling and a ground, attach both the Rigidbody and Collider Component in both objects.
On the ground one, set the rigidody to “isKinematic”

Hope this help.