How can I put a limit on "in-air dashes?"

I've created a little 2D project where my player only moves with short dash movements, which I've created using the script from this video: https://www.youtube.com/watch?v=w4YV8s9Wi3w What I want to do is create a way for my player to maintain the ability to dash directly upwards into the air, but I want the player to only have a limited number of dashes whilst they remain airborne. I've been trying to change parts of this video's (https://www.youtube.com/watch?v=QGDeafTx5ug) code to make it work with my existing 'dashMove' script, but I'm not proficient enough with coding to know what my next steps should be.

I should probably mention that the way I'm trying to limit the in-air dashes is with 'isGrounded' script from the second video (2D Double/Triple Jump) Any help would be greatly appreciated :)

My code:

using System.Collections; using System.Collections.Generic; using UnityEngine;

public class DashMove : MonoBehaviour {

 private Rigidbody2D rb;
 public float dashSpeed;
 private float dashTime;
 public float startDashTime;
 private int direction;
 public Animator animator;

 // classes for testing if the player is touching the ground
 private bool isGrounded;
 public Transform groundCheck; // the actual ingame object that is attatched to the character.
 public float checkRadius;
 public LayerMask whatIsGround; // added a layer in unity called 'Ground' and put all my 'ground peices' on this layer

 private int airMove; // in tutorial this was called 'extraJumps' but fot the purposes of my game, I changed it to better reflect the functionally I am trying to create
 public int midAirValue;

 // Use this for initialization
 void Start () {

     airMove = midAirValue;

     rb = GetComponent<Rigidbody2D>();

     animator = GetComponent<Animator>();

     dashTime = startDashTime;
 }
 
 // Update is called once per frame
 void Update () {

     isGrounded = Physics2D.OverlapCircle(groundCheck.position, checkRadius, whatIsGround);

     if (isGrounded == true){
         airMove = midAirValue;
     }

     if (Input.GetKeyDown(KeyCode.LeftArrow, KeyCode.RightArrow, KeyCode.UpArrow, KeyCode.DownArrow) && airMove > 0) // apparently 'GetKeyDown' needs 4 arguments, but as far as i'm aware, i've provided 4 arguments in the brackets, with the 4 KeyCodes...
     {
         rb.velocity = Vector2.up * dashSpeed; // these are the parts where I think i'm going pretty wrong. I'm pretty sure the 'Vector2.up' is completely wrong for what i'm trying to do, and I'm not 100% on whether 'dashSpeed' is the right class to use here either.
         airMove--;
     }
     else if (Input.GetKeyDown(KeyCode.LeftArrow, KeyCode.RightArrow, KeyCode.UpArrow, KeyCode.DownArrow) && airMove == 0 && isGrounded == true) // apparently 'GetKeyDown' needs 4 arguments, but as far as i'm aware, i've provided 4 arguments in the brackets, with the 4 KeyCodes...
     {
         rb.velocity = Vector2.up * dashSpeed; // these are the parts where I think i'm going pretty wrong. I'm pretty sure the 'Vector2.up' is completely wrong for what i'm trying to do, and I'm not 100% on whether 'dashSpeed' is the right class to use here either.
     }

     if (direction == 0) {
         if (Input.GetKeyDown(KeyCode.LeftArrow)) {
             direction = 1;
         } else if (Input.GetKeyDown(KeyCode.RightArrow)) {
             direction = 2;
         } else if (Input.GetKeyDown(KeyCode.UpArrow)) {
             direction = 3;
         } else if(Input.GetKeyDown(KeyCode.DownArrow)) {
             direction = 4;
         }
     } else {
         if(dashTime <= 0) {
             direction = 0;
             dashTime = startDashTime;
             rb.velocity = Vector2.zero;

             // reset animation bools ??
             animator.SetBool("DashLeft", false);
             animator.SetBool("DashRight", false);
             animator.SetBool("DashUp", false);
             animator.SetBool("DashDown", false);


         }
         else {
             dashTime -= Time.deltaTime;

             if(direction == 1){
                 rb.velocity = Vector2.left * dashSpeed;
                 animator.SetBool("DashLeft", true);

             } else if(direction == 2){
                 rb.velocity = Vector2.right * dashSpeed;
                 animator.SetBool("DashRight", true);

             } else if(direction == 3){
                 rb.velocity = Vector2.up * dashSpeed;
                 animator.SetBool("DashUp", true);

             } else if(direction == 4){
                 rb.velocity = Vector2.down * dashSpeed;
                 animator.SetBool("DashDown", true);

             }
         }
     }
 }

}