My 2d game jump only one time

using UnityEngine; using System.Collections; using System.Drawing;

public class PlayerMovement : MonoBehaviour {

 private bool Ground = true;
 public float speed;               
 private Rigidbody2D Player;        

 public float jumpPower;
 

   
 void Start()
 {
     Player = GetComponent<Rigidbody2D>();
     
 }

  
 void FixedUpdate()
 {
   
     float moveHorizontal = Input.GetAxis("Horizontal");

     
     float moveVertical = Input.GetAxis("Vertical");

    
     Vector2 movement = new Vector2(moveHorizontal, moveVertical);

 
     Player.AddForce(movement * speed);

     if (Input.GetKey(KeyCode.RightArrow))
         transform.Translate(Vector3.right * speed * Time.deltaTime);
     if (Input.GetKey(KeyCode.LeftArrow))
         transform.Translate(-Vector2.right * speed * Time.deltaTime);

     GetComponent<Rigidbody2D>();

     if (Input.GetKey(KeyCode.W) && Ground == true)
     {
         Player.AddForce(Vector2.up * jumpPower);
         Ground = false;

     }
     Player.AddForce(new Vector2(0, -9.8f));


     
 }
 private void OnCollisionStay2D(Collision2D gg)
 {
     if (gg.gameObject.tag == "GrassThinSprite")

     {
         Ground = true;
     }
 }

} ,using UnityEngine; using System.Collections; using System.Drawing;

public class PlayerMovement : MonoBehaviour {

 private bool Ground = true;
 public float speed;              

 private Rigidbody2D Player;      

 public float jumpPower;
 


 void Start()
 {
     Player = GetComponent<Rigidbody2D>();
     
 }

 
 void FixedUpdate()
 {
    
     float moveHorizontal = Input.GetAxis("Horizontal");

    
     float moveVertical = Input.GetAxis("Vertical");

    
     Vector2 movement = new Vector2(moveHorizontal, moveVertical);

     
     Player.AddForce(movement * speed);

     if (Input.GetKey(KeyCode.RightArrow))
         transform.Translate(Vector3.right * speed * Time.deltaTime);
     if (Input.GetKey(KeyCode.LeftArrow))
         transform.Translate(-Vector2.right * speed * Time.deltaTime);

     GetComponent<Rigidbody2D>();

     if (Input.GetKey(KeyCode.W) && Ground == true)
     {
         Player.AddForce(Vector2.up * jumpPower);
         Ground = false;

     }
     Player.AddForce(new Vector2(0, -9.8f));


     
 }
 private void OnCollisionStay2D(Collision2D gg)
 {
     if (gg.gameObject.tag == "GrassThinSprite")

     {
         Ground = true;
     }
 }

}