I have a weird error message i don't understand

Assets/BallControl.js(9,30): BCE0024: The type ‘UnityEngine.Rigidbody’ does not have a visible constructor that matches the argument list ‘(UnityEngine.Vector3)’. what does that mean?

It means that, on line 9 of the BallControl.js script, you’re trying to call:

Instantiate (SomeRigidbody, SomeVector3);

You need to supply a rotation for the instantiated object as the third parameter - use Quaternion.identity if you’re not sure.

It’s all in the manual:

And you might want to watch: https://unity3d.com/learn/tutorials/modules/beginner/scripting/instantiate