Player Falls Extremely Slowly While Moving In Air After Jump(Closed)

So in unity I’m making a 2D platformer and I’m adding jumping. But when the player moves in the air it falls extremely slowly then falls fast again when I stop walking in the air! I have no idea how to fix this problem! I’m not coding gravity I’m using the built in rigidbody gravity.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
using UnityEngine.SceneManagement;

public class Movement : MonoBehaviour
{
    public float speedright = 5;
    public Rigidbody2D rb;
    public float speedleft = -50;
    public Text e;
    Scene currentScene;
    string sceneName;
    public float jumpheight = 300;
    public Talking script;

    void Start()
    {
        Cursor.visible = false;
        Cursor.lockState = CursorLockMode.Locked;
        rb.constraints = RigidbodyConstraints2D.FreezeRotation;
        bool Seen = false;
        Invoke("Starting", 3);
        if(Seen == true)
        {
            script.CanMove = 1;
        }
    }

    private void OnTriggerStay2D(Collider2D collider)
    {
        if (sceneName == "Bedroom"){
            e.text = "E To Interact";
            e.gameObject.SetActive(true);
            if(Input.GetKeyDown("e"))
            {
                SceneManager.LoadScene("Hallway");
            }
        }
    }
    private void OnTriggerExit2D()
    {
        e.text = "";
    }

    void Update()
    {
        if (script.CanMove == 1)
        {
            if (Input.GetKey("d"))
            {
                rb.velocity = new Vector2(speedright, 0 * Time.deltaTime);
                rb.transform.eulerAngles = new Vector3(0, 0, 0);
            }

            if (Input.GetKey("a"))
            {
                rb.velocity = new Vector2(speedleft, 0 * Time.deltaTime);
                rb.transform.eulerAngles = new Vector3(0, 180, 0);
            }

            if (Input.GetKeyDown(KeyCode.Space))
            {
                rb.AddForce(Vector2.up * jumpheight, ForceMode2D.Impulse);
            }
        }
    }
}

>Solution :

You are setting the y velocity to 0 in each iteration of Update(). Maybe try something like

float currentYVelocity = rb.velocity.y; 

if (Input.GetKey("d"))
{
    rb.velocity = new Vector2(speedright, currentYVelocity);
    rb.transform.eulerAngles = new Vector3(0, 0, 0);
}

if (Input.GetKey("a"))
{
    rb.velocity = new Vector2(speedleft, currentYVelocity);
    rb.transform.eulerAngles = new Vector3(0, 180, 0);
}

At least, change 0 * Time.deltaTime to some value non zero.

Disclaimer: I have never used Unity, I am just making an observation