How do I fix my dash - it only works sometimes - unity3d

Question

i started my first game project and i'm stuck with my dash
my dash randomly starts working when i press dash button (R) but it's not always working. i'm new to the gamedev and tried looking for solutions - like FixedUpdate or AddForce or transform.position - but nothing helps. if you have any ideas could you help me?
my code is below
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class PlayerMovement : MonoBehaviour
{
private Rigidbody2D rb;
private BoxCollider2D coll;
private int jumpCount = 1;
private bool canDash = true;
private bool isDashing;
[SerializeField] private LayerMask jumpableGround;
// Start is called before the first frame update
private void Start()
{
rb = GetComponent<Rigidbody2D>();
coll = GetComponent<BoxCollider2D>();
}
// Update is called once per frame
private void Update()
{
float dirX = Input.GetAxisRaw("Horizontal");
rb.velocity = new Vector2(dirX * 7f, rb.velocity.y);
if (Input.GetButtonDown("Jump") && jumpCount != 0)
{
rb.velocity = new Vector2(rb.velocity.x, 12f);
jumpCount--;
}
if (IsGrounded())
{
jumpCount = 1;
}
if(Input.GetKeyDown(KeyCode.R) && canDash)
{
_ = StartCoroutine(Dash());
}
}
private bool IsGrounded()
{
return Physics2D.BoxCast(coll.bounds.center, coll.bounds.size, 0f, Vector2.down, .1f, jumpableGround);
}
private IEnumerator Dash()
{
canDash = false;
float originalGravity = rb.gravityScale;
rb.gravityScale = 0f;
rb.velocity = new Vector2(rb.velocity.x, 0f);
rb.AddForce(new Vector2(rb.velocity.x * 24f, 0f), ForceMode2D.Impulse);
Debug.Log("something");
rb.gravityScale = originalGravity;
yield return new WaitForSeconds(0.1f);
canDash = true;
}
}

Answer 1

It looks like you are overriding the velocity on each call to Update():
rb.velocity = new Vector2(dirX * 7f, rb.velocity.y);
You can probably add a field for "_isDashing", and if the user is dashing don't override the velocity.
If you're not fully using the built in physics engine, you may need to also track the dash direction. For example some logic like "If not dashing, update velocity as normal. If dashing, update velocity and dash direction to appropriate settings".