Hello CR-Safari!
Please use code tags when you paste code, makes it much more readable: Using code tags properly
Now regarding your problem, at no point you’re setting your ballMoving boolean back to false, so the following code is executed only once:
if (Input.GetButtonDown("Jump") & ballMoving == false)
{
ballMoving = true;
rb.AddForce(Vector2.up * ballSpeed);
}
That would explain why you see the value increasing in the Inspector but not see the ball moving faster.