Rigidbody doesn't work with my script

Hello, sorry if my English isn't good because I'm French.

I did a script for my player (a sphere) w$$anonymous$$ch I can control it by using a joystick. When I put my script in my sphere, everyt$$anonymous$$ng works perfectly. Then I add a rigidbody as a component to my sphere for the gravity. But the problem is that my sphere doesn't want to fall, and t$$anonymous$$s one is turning around itself quickly... I don't know why...

My script is following :

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class PlayerMotor : BaseMotor
 {
     public VirtualJoystick joystick;
     protected override void UpdateMotor()
     {
         // Get the input
         MoveVector = InputDirection();
 
         // Send the input to a filler 
         MoveVector = state.ProcessMotion(MoveVector);
 
         // Move
         Move();
     }
 
     private Vector3 InputDirection()
     {
         Vector3 dir = Vector3.zero;
 
     //    dir.x = Input.GetAxis ("Horizontal"); 
     //    dir.z = Input.GetAxis ("Vertical");
 
         dir.x = joystick.Horizontal();
         dir.z = joystick.Vertical();
 
         if (dir.magnitude > 1)
             dir.Normalize();
         return dir;
     }
 }

When I uncheck "script" in my sphere, everyt$$anonymous$$ng works.

Thank you !