please, use code tag, it’s impossible to read otherwise. Using code tags properly
On a brief overview,
jumpVelocity -= gravity * Time.deltaTime;
without the delta time you’re subtracting the full amount of gravity in m/s PER FRAME, if you’re running at 60 FPS and earth-like gravity with unity units as metric units the gravity will be equivalent to 9.81 * 60, just short of 600.
also, how are you using rigidbodies if your manipulating the transform directly?
didn’t really follow your code all the way, did you just experiment with it?