How to fix a infinity jump?

How can i stop the infinity jump in my script? Here is

public class PlayerMovement : MonoBehaviour
{

    private Joystick joystick;
    private Joybutton joybutton;

    private CharacterController controller;
    private Vector3 playerVelocity;

    private bool groundedPlayer;

    public float playerSpeed = 5.0f;
    public float jumpHeight = 1.0f;
    private float gravityValue = -9.81;

    private void Start()
    {
        controller = gameObject.GetComponent<CharacterController>();
        joystick = FindObjectOfType<Joystick>();
        joybutton = FindObjectOfType<Joybutton>();
    }

    void Update()
    {
        groundedPlayer = controller.isGrounded;
        if (groundedPlayer && playerVelocity.y < 0)
        {
            playerVelocity.y = 0f;
        }

        Vector3 move = new Vector3(joystick.Horizontal , 0, joystick.Vertical);
        controller.Move(move * Time.deltaTime * playerSpeed);

        if (move != Vector3.zero)
        {
            gameObject.transform.forward = move;
        }

        if (joybutton.Pressed && groundedPlayer)
        {
            playerVelocity.y += Mathf.Sqrt(jumpHeight * -3.0f * gravityValue);
        }

        playerVelocity.y += gravityValue * Time.deltaTime;
        controller.Move(playerVelocity * Time.deltaTime);
    }
}

Do you mean that you want to prevent the player from jumping mid-air?
So, completely out of my mind, if I were you, @SherqPl ,
I would add this to my code:

void OnCollisionEnter (Collision col)
{
if(col.gameObject.tag == "Ground")
{
groundedPlayer = true;
}
}

and change this…

if (joybutton.Pressed && groundedPlayer)
{
        playerVelocity.y += Mathf.Sqrt(jumpHeight * -3.0f * gravityValue);
}

to this:

if (joybutton.Pressed && groundedPlayer)
{
      playerVelocity.y += Mathf.Sqrt(jumpHeight * -3.0f * gravityValue);
      groundedPlayer = false;
}

Don’t forget to create a new tag called “Ground” and assigning it to your ground plane/cube etc.

I haven’t tested your code out, but it worked for all my other projects, so it should work in your case too.