Why my Character's wall jump looks like teleport?

Hi guys, I'm a beginner of Unity and don't have any background of coding, I learn it by unity learning and youtube only.

Now I have a problem of wall jump, my character can't jump smoothly opposite to the wall, it looks like teleport horizontally and didn't move upward like image below, here is my coding:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class Player : MonoBehaviour
 {
     private Rigidbody2D rb;
     public float speed = 20;
 
     private bool facingRight = true;
 
     public float jumpVelocity = 25;
     private bool isGround;
     public Transform groundCheck1;
     public Transform groundCheck2;
     public LayerMask defineGround;
 
     private bool isWall;
     public Transform wallCheckLeft;
     public Transform wallCheckRight;
     public float wallCheckRadius;
     public float slideDown = -3;
     public float wallGrabSpeed = 10;
     public float wallGrabTime = 2;
 
     private bool wallJumping = false;
     
 
     // Start is called before the first frame update
     void Start()
     {
         rb = GetComponent<Rigidbody2D>();
     }
 
     // Update is called once per frame
     void Update()
     {
         float x = Input.GetAxis("Horizontal");
         float y = Input.GetAxis("Vertical");
         Vector2 dir = new Vector2(x, y);
         
         if (x > 0 && facingRight == false)
         {
             Flip();
         }
         else if( x < 0 && facingRight == true)
         {
             Flip();
         }
 
         Walk(dir);
 
         isGround = Physics2D.OverlapArea(groundCheck1.position, groundCheck2.position, defineGround);
 
         isWall = Physics2D.OverlapCircle(wallCheckLeft.position, wallCheckRadius, defineGround) || Physics2D.OverlapCircle(wallCheckRight.position, wallCheckRadius, defineGround);
 
         if (Input.GetButtonDown("Jump"))
         {
             Jump();
         }
         if (Input.GetButtonDown("Jump") && isGround != true && isWall == true)
         {
             wallJumping = true;
             Invoke("SetwallJumpingToFalse", 0.01f);
         }
         if (wallJumping)
         {
             rb.velocity = new Vector2(-rb.velocity.x * speed, jumpVelocity);
         }
 
 
         if (isGround == true)
         {
             wallGrabTime = 2;
         }
         if (isWall == true && Input.GetButton("Horizontal"))
         {
             WallGrab();
         }
     }
     
     private void Walk(Vector2 dir)
     {
         rb.velocity = (new Vector2(dir.x * speed, rb.velocity.y));
     }
 
     private void Jump()
     {
         if (isGround == true)
         {
             rb.velocity = (new Vector2(rb.velocity.x, jumpVelocity));
         }
     }
 
     void SetwallJumpingToFalse()
     {
         wallJumping = false;
     }
 
 
     private void WallGrab()
     {
         
         if (Input.GetButton("Vertical") && wallGrabTime > 0)
         {
             rb.velocity = (new Vector2(rb.velocity.x, slideDown + wallGrabSpeed));
             wallGrabTime -= Time.deltaTime;
         }
         
     }
 
     private void Flip()
     {
         transform.localScale = new Vector2(-transform.localScale.x, transform.localScale.y);
         facingRight = !facingRight;
     }
 
 }

Please forgive me why I don't use other solved answer's coding, I just want to know what's wrong to my coding, why it can't work smoothly and how should I solve this...thanks.