2D Jumping System not working correctly - Unity 2D

Question

I was working on my 2D game in unity and i made this system to set the character to jump, and move around, but for some reason, i can only move mid air when i was moving on the ground, but if i stand still and then jump, i can not move mid air

Further Explaination: imagine you want to pick a coin in the air, and there is an obstacle under the coin, thus you have to jump while moving forward to pick it up, my problem is that you can only move mid air, if you were moving on the floor originally, but if you jump and THEN move right or left, the system just ignores it

My code:

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

[RequireComponent(typeof(Rigidbody2D))]
[RequireComponent(typeof(CapsuleCollider2D))]

public class CharacterController2D : MonoBehaviour
{
    // Move player in 2D space
    public float maxSpeed = 3.4f;
    public float jumpHeight = 6.5f;
    public float gravityScale = 1.5f;
    public Camera mainCamera;

    bool facingRight = true;
    float moveDirection = 0;
    bool isGrounded = false;
    Vector3 cameraPos;
    Rigidbody2D r2d;
    CapsuleCollider2D mainCollider;
    Transform t;

    // Use this for initialization
    void Start()
    {
        t = transform;
        r2d = GetComponent<Rigidbody2D>();
        mainCollider = GetComponent<CapsuleCollider2D>();
        r2d.freezeRotation = true;
        r2d.collisionDetectionMode = CollisionDetectionMode2D.Continuous;
        r2d.gravityScale = gravityScale;
        facingRight = t.localScale.x > 0;

        if (mainCamera)
        {
            cameraPos = mainCamera.transform.position;
        }
    }

    // Update is called once per frame
    void Update()
    {
        // Movement controls
        if ((Input.GetKey(KeyCode.A) || Input.GetKey(KeyCode.D)) && (isGrounded || Mathf.Abs(r2d.velocity.x) > 0.01f))
        {
            moveDirection = Input.GetKey(KeyCode.A) ? -1 : 1;
        }
        else
        {
            if (isGrounded || r2d.velocity.magnitude < 0.01f)
            {
                moveDirection = 0;
            }
        }

        // Change facing direction
        if (moveDirection != 0)
        {
            if (moveDirection > 0 && !facingRight)
            {
                facingRight = true;
                t.localScale = new Vector3(Mathf.Abs(t.localScale.x), t.localScale.y, transform.localScale.z);
            }
            if (moveDirection < 0 && facingRight)
            {
                facingRight = false;
                t.localScale = new Vector3(-Mathf.Abs(t.localScale.x), t.localScale.y, t.localScale.z);
            }
        }

        // Jumping
        if (Input.GetKeyDown(KeyCode.W) && isGrounded)
        {
            r2d.velocity = new Vector2(r2d.velocity.x, jumpHeight);
        }

        // Camera follow
        if (mainCamera)
        {
            mainCamera.transform.position = new Vector3(t.position.x, cameraPos.y, cameraPos.z);
        }
    }

    void FixedUpdate()
    {
        Bounds colliderBounds = mainCollider.bounds;
        float colliderRadius = mainCollider.size.x * 0.4f * Mathf.Abs(transform.localScale.x);
        Vector3 groundCheckPos = colliderBounds.min + new Vector3(colliderBounds.size.x * 1f, colliderRadius * 0.9f, 0);
        // Check if player is grounded
        Collider2D[] colliders = Physics2D.OverlapCircleAll(groundCheckPos, colliderRadius);
        //Check if any of the overlapping colliders are not player collider, if so, set isGrounded to true
        isGrounded = false;
        if (colliders.Length > 0)
        {
            for (int i = 0; i < colliders.Length; i++)
            {
                if (colliders[i] != mainCollider)
                {
                    isGrounded = true;
                    break;
                }
            }
        }

        // Apply movement velocity
        r2d.velocity = new Vector2((moveDirection) * maxSpeed, r2d.velocity.y);

        // Simple debug
        Debug.DrawLine(groundCheckPos, groundCheckPos - new Vector3(0, colliderRadius, 0), isGrounded ? Color.green : Color.red);
        Debug.DrawLine(groundCheckPos, groundCheckPos - new Vector3(colliderRadius, 0, 0), isGrounded ? Color.green : Color.red);
    }
}```

Answer 1

if ((Input.GetKey(KeyCode.A) || Input.GetKey(KeyCode.D)) && (isGrounded || Mathf.Abs(r2d.velocity.x) > 0.01f))

In this line you check if you are grounded isGrounded or have some horizontal velocity Mathf.Abs(r2d.velocity.x) > 0.01f .
If you have any of those you give horizontal control.
So if you are moving horizontal en then jump Mathf.Abs(r2d.velocity.x) > 0.01f is true and gives you control in the air.
But if you are standing still and the jump isGrounded is false bequase you are in the air and Mathf.Abs(r2d.velocity.x) > 0.01f is false so you cant control your jump in the air.
If you always want control in the air remove the (isGrounded || Mathf.Abs(r2d.velocity.x) > 0.01f) check