double jump

so, im fairly new to coding (i just started back up, so im pretty fuckin rusty), and i forget how to make my character double jump, this script has a wonky double jump, im looking for a clean and smooth double jump(not sure if i should share my whole code or just the jumping so ill do the entire code), this is for a 2d platformer game by the way(most of this code is pretty much stolen and edited, im bad i know lol), oh and the flip mechanic doesnt work idk why

using UnityEngine;

public class PlayerController : MonoBehaviour {

 public float speed;
 public float jump;
 float moveVelocity;
  

 bool grounded = true;
 void Update()
 {
     //Jumping
     if (Input.GetKeyDown(KeyCode.Space) || Input.GetKeyDown(KeyCode.UpArrow) || Input.GetKeyDown(KeyCode.Z) || Input.GetKeyDown(KeyCode.W))
     {
         if (grounded)
         {
             GetComponent<Rigidbody2D>().velocity = new Vector2(GetComponent<Rigidbody2D>().velocity.x, jump);
         }

     }
     moveVelocity = 0;
     //Horizontal/Left and Right Movement
     if (Input.GetKey(KeyCode.LeftArrow) || Input.GetKey(KeyCode.A))
     {
         moveVelocity = -speed;
     }
     if (Input.GetKey(KeyCode.RightArrow) || Input.GetKey(KeyCode.D))
     {
         moveVelocity = speed;
     }
     GetComponent<Rigidbody2D>().velocity = new Vector2(moveVelocity, GetComponent<Rigidbody2D>().velocity.y);
 }
 private void OnCollisionEnter2D(Collision2D collision)
 {
     if (collision.gameObject.CompareTag("Ground"))
     {
         grounded = true;
     }
 }

}