double jumping after falling off edge problem

so i spend i dont know how long trying to make double jump work after falling off an edge but its simple not happening so i wonder if anyone has any idea how to do

this is my code

 // jumping variables
     public float jumpCount;
     public bool allowJump;
     public float jump;
 
     // rigidbody name
     private Rigidbody2D myrigidbody2d;
 
     // ground checking varaibles
     public Transform ground_check;
     public float ground_check_radius;
     public LayerMask what_is_ground;
     public bool grounded;
 
     void Start ()
     {
         myrigidbody2d = FindObjectOfType<Rigidbody2D> ();
     }
 
     void FixedUpdate ()
     {
         // checks fro ground
         grounded = Physics2D.OverlapCircle (ground_check.position, ground_check_radius, what_is_ground);
     }
 
     // Update is called once per frame
     void Update () {
         // jump when space is pressed
         if (Input.GetKeyDown (KeyCode.Space)) {
             
             // single jump
             if (jumpCount == 0f)
             {
                 jumpCount++;
                 jump_code ();
             }
             
             // double jump
             else if (jumpCount == 1f)
             {
                 jump_code ();
                 jumpCount++;
             }
         }
 
         // resetst the jump count once grouped
         if (grounded)
         {
             jumpCount = 0f;
         }
     }
 
     // jump code
     public void jump_code()
     {
         if (allowJump)
         {
             myrigidbody2d.velocity = new Vector2 (myrigidbody2d.velocity.x, jump);
             GetComponent<AudioSource>().Play();
         }
     }

so what this code does is that instead of solving my problem it just gives you triple jump when jumping from ground and double jump when falling off an edge i have no idea why help plz