How do i increase Speed while running 2d

Yoh guys, i have two issues, the first is that when i run even if I release the key (R) the character keeps running, the second is that I can not grow the speed: so both when walking and when running, the speed remains the same. Someone can help me?

public class Movement : MonoBehaviour
{

public float speedmultiplier = 100.0f;

public float runSpeed = 50f;
public Rigidbody2D rb2d;
private float currentMaxSpeed;
bool facingRight = true;
public float speed= 10f;
public Animator animator;

// Use this for initialization

void Start () 

{
animator = GetComponent<Animator> ();
rb2d = GetComponent<Rigidbody2D> ();

}

void Update ()
{
		

	if (Input.GetKey (KeyCode.D)) 
	{
		transform.Translate (new Vector2 (1, rb2d.velocity.y) * Time.deltaTime * speedmultiplier);
	} 

	else if (Input.GetKey (KeyCode.A)) 
	{
		transform.Translate (new Vector2 (-1, rb2d.velocity.y) * Time.deltaTime * speedmultiplier);
	}

	if (Input.GetAxis ("Horizontal") > 0 && !facingRight) 

	{
		rb2d.AddForce (transform.right * speedmultiplier);

		Flip ();

		animator.Play ("Walk");

	} 

	if (Input.GetAxis ("Horizontal") < 0 && facingRight) 

	{
		rb2d.AddForce (transform.right * speedmultiplier);

		Flip ();

		animator.Play ("Walk");
	} 

		else if (Input.GetAxisRaw ("Horizontal") == 0) 
		
		{
			rb2d.velocity = new Vector2 (0, rb2d.velocity.y);
			animator.Play ("Idle");
		}

	if (Input.GetKey (KeyCode.R)) 
	
	{
		animator.speed = 30f;

		animator.Play ("Run");

		bool Run = true;

		rb2d.AddForce (transform.right * speedmultiplier);

	}
			
			
		float speed = currentMaxSpeed * Input.GetAxis ("Horizontal");
		animator.SetFloat ("speed", Mathf.Abs (speed));
		transform.Translate (Vector2.right * speed * Time.deltaTime);
	    
		
}

	void Flip()

	{
		facingRight = !facingRight;
		Vector3 theScale = transform.localScale;
		theScale.x *= -1;
		transform.localScale = theScale;
	}

}

You need to have a variable for changing speed when running, keep the variable at 1f and multiply it by the final force you give the rigidbody for speed, then if you increase that value like make it 2f, the speed will be 2x faster.