When i press space, my character is flying in unity 2d

Question

I did a jump script. But when i press space, my character first jumping, and after flying forever. And i get this problem my almost all projects. How can i fix this?

My script:

    Rigidbody2D rb;
    public float speed = 2.5f;
    public float jumpSpeed = 50f;
    bool isJump = false;
    // Start is called before the first frame update
    void Start()
    {
        rb = GetComponent<Rigidbody2D>();
    }

    // Update is called once per frame
    void Update() {
                    float horizontal = Input.GetAxis("Horizontal");
            float vertical = Input.GetAxis("Vertical");
            Vector3 force = new Vector3(horizontal,rb.velocity.y,vertical);
            rb.AddForce(force*speed);

            
            if(Input.GetKeyDown(KeyCode.Space)){
                if(isJump == false)
                {
                    rb.velocity = Vector2.up * jumpSpeed;
                    isJump = true;
                }
        }
    }
    private void OnCollisionEnter2D(Collision2D other) {
            isJump = false;
        }