Movement and Rotation - unity3d

Question

So I'm currently learning Unity 3D but I stuck on a problem.
So Iv'e done this code that the player moves with WASD keys. The movement works fine.
I tried to aply some rotation, that way the player can turn back or move to different positions.
But the problem is, I put the rotarion and the player turns but when he does he swap W for S, so basically if I turn back, when I press W to go forward he go backward and when I press S instead of going Backward he goes Forward.
I don't to make a lot of changes in my code because I think it's very "basic" right now and easy to understand. So if someone can explain what I'm doing wrong I would appreciate.
using System.Collections.Generic;
using UnityEngine;
//[RequireComponent(typeof(Rigidbody))]
public class PlayerMov : MonoBehaviour
{
//Player mov speed
float MovSpeed = 10f;
//Player jump, jumpforce, check if is on the ground and rb(rigidbody component)
public Vector3 jump;
public float jumpForce = 2.0f;
public bool isGrounded;
Rigidbody rb;
public float TurnSpeed = 100f;
void Start()
{
rb = GetComponent<Rigidbody>();
jump = new Vector3(0.0f, 2.0f, 0.0f);
}
void OnCollisionStay()
{
isGrounded = true;
}
void Update()
{
if (Input.GetKey(KeyCode.W))
{
transform.position -= Vector3.forward * MovSpeed * Time.deltaTime;
//transform.Translate(Vector3.forward * MovSpeed * Time.deltaTime);
}
if (Input.GetKey(KeyCode.A))
{
transform.position -= Vector3.left * MovSpeed * Time.deltaTime;
}
if (Input.GetKey(KeyCode.S))
{
transform.position -= Vector3.back * MovSpeed * Time.deltaTime;
//transform.Translate(-Vector3.forward * MovSpeed * Time.deltaTime);
}
if (Input.GetKey(KeyCode.D))
{
transform.position -= Vector3.right * MovSpeed * Time.deltaTime;
transform.Rotate(Vector3.up * TurnSpeed * Time.deltaTime);
}
if (Input.GetKeyDown(KeyCode.Space) && isGrounded)
{
rb.AddForce(jump * jumpForce, ForceMode.Impulse);
isGrounded = false;
}
if (Input.GetKey(KeyCode.LeftArrow))
{
transform.Rotate(Vector3.up * TurnSpeed * Time.deltaTime);
}
if (Input.GetKey(KeyCode.RightArrow))
{
transform.Rotate(Vector3.up * TurnSpeed * Time.deltaTime);
}

Answer 1

Why not use the Translate method? Please see its documentation. You can define a which space you want the transform to move in (global or local)
https://docs.unity3d.com/ScriptReference/Transform.Translate.html
As a side note: why check for each separate key? Using Input.GetAxis("Horizontal") and Input.GetAxis("Horizontal") vertical would be simpler.