Adding in a system to check for player death.

Hello, I am new here and I was wanting to add a system to my script that checks if the player has died from collision or not.
Below is my script

public class Guy : MonoBehaviour{

void Update()
{
    Movement();
}

void Movement()
{
    if (Input.GetKey(KeyCode.D))
    {
        transform.Translate(Vector2.right * 4f * Time.deltaTime);
        transform.eulerAngles = new Vector2(0, 0);
    }
    if (Input.GetKey(KeyCode.A))
    {
        transform.Translate(Vector2.right * 4f * Time.deltaTime);
        transform.eulerAngles = new Vector2(0, 180);
    }
}

}

and here is one that has something similar to what I am trying to achieve.

public class Bird : MonoBehaviour
{
public float upForce; //Upward force of the “flap”.
private bool isDead = false; //Has the player collided with a wall?

private Animator anim;                  //Reference to the Animator component.
private Rigidbody2D rb2d;               //Holds a reference to the Rigidbody2D component of the bird.

void Start()
{
    //Get reference to the Animator component attached to this GameObject.
    anim = GetComponent<Animator> ();
    //Get and store a reference to the Rigidbody2D attached to this GameObject.
    rb2d = GetComponent<Rigidbody2D>();
}

void Update()
{
    //Don't allow control if the bird has died.
    if (isDead == false) 
    {
        //Look for input to trigger a "flap".
        if (Input.GetMouseButtonDown(0)) 
        {
            //...tell the animator about it and then...
            anim.SetTrigger("Flap");
            //...zero out the birds current y velocity before...
            rb2d.velocity = Vector2.zero;
            //  new Vector2(rb2d.velocity.x, 0);
            //..giving the bird some upward force.
            rb2d.AddForce(new Vector2(0, upForce));
        }
    }
}

void OnCollisionEnter2D(Collision2D other)
{
    // Zero out the bird's velocity
    rb2d.velocity = Vector2.zero;
    // If the bird collides with something set it to dead...
    isDead = true;
    //...tell the Animator about it...
    anim.SetTrigger ("Die");
    //...and tell the game control about it.
    GameControl.instance.BirdDied ();
}

}

I thought a Boolean would do the trick as a simple true or false for the player death, but maybe I am misplacing the boolean in the script, because after adding it in my player does not move at all.

public class Guy : MonoBehaviour{

private bool isDead = false;
    
void Update()
{
 Movement();
}

void Movement()
{
    if (isDead =false)
    { 
    if (Input.GetKey(KeyCode.D))
    {
        transform.Translate(Vector2.right * 4f * Time.deltaTime);
        transform.eulerAngles = new Vector2(0, 0);
    }
    if (Input.GetKey(KeyCode.A))
    {
        transform.Translate(Vector2.right * 4f * Time.deltaTime);
        transform.eulerAngles = new Vector2(0, 180);
    }
}

}
}