Extremely simple car movement

Hello, I’m trying to make a game like Cubed Rally Racer which has very simple car movement like you can see in the video, I tried to look at the car tutorial and other answers here about cars but I couldn’t find what I was looking for.

What I have at the moment is a simple cube, with a rigidbody and 1 of mass(it won’t move with more than 1 of mass), and 4 spheres with wheel colliders on them under the cube and this is my movement script:

function Update () {
if (Input.GetKey(KeyCode.W))
	rigidbody.AddForce (transform.forward * 100 * Time.deltaTime);
if (Input.GetKey(KeyCode.S))
	rigidbody.AddForce (-(transform.forward) * 4*Time.deltaTime);
if (Input.GetKey(KeyCode.D))
if (Input.GetKey(KeyCode.A))


It applies a force to the rigidbody to make it move forward, the “steering” is working but the car flips over as soon as it has some speed and it tries to steer, also the car won’t stop moving once it has received some force (it seems like there’s no friction).
How do I make the car more stable and add friction to make it stop when it stops receiving force?

I found out there’s an online version of the game to see how the movement works:

2d movement script I used.

using UnityEngine;
using System.Collections;

public class carMove : MonoBehaviour {
	float xspeep = 0f;
	float power = 0.001f;
	float friction = 0.95f;
	bool right = false;
	bool left = false;
	public float fuel = 2;
	// Use this for initialization
	void FixedUpdate () {
			xspeep += power;
			fuel -= power;
			xspeep -= power;
			fuel -= power;
	// Update is called once per frame
	void Update () {
			right = true;
			right = false;
			left = true;
			left = false;
		if(fuel < 0){
			xspeep = 0;
		xspeep *= friction;
		transform.Translate(Vector3.right * -xspeep);