I have problem.

When i apply this script

 using UnityEngine;
   using System.Collections;
      
 public class Volo : MonoBehaviour {
    public Vector2 jumpForce = new Vector2(0, 300);
    float flightSpeed = 10.0f; // Set this speed to whatever you want.
    float energyDecay = 1.0f; // Set this to whatever you want.
    float energy;
      const float maxEnergy = 100;
      bool grounded;
      
      void Update ()
      {
           Vector2 jumpForce = new Vector2(0, 300);
          if (Input.GetKeyDown("space") && grounded) // Controls the initial jump
          {
              GetComponent<Rigidbody2D>().velocity = Vector2.zero;
              GetComponent<Rigidbody2D>().AddForce(jumpForce);
          }
      if (Input.GetKey("space") && energy > 0) // Controls flight for as long as space is held down
          {
    Vector2 v = GetComponent<Transform>().velocity; // Creates a temporary velocity variable
    v.y = flightSpeed; // Sets the temporary variables Y velocity to the flightSpeed
     GetComponent<Transform>().velocity = v; // Sets the character velocity to the flightSpeed
   energy -= energyDecay; // Reduces energy by energyDecay every frame
          }
      }
      
      void OnCollisionEnter(Collision col) // When the character collides with something
      {
          if(col.collider.tag == "ground") // If the object has the tag "ground"
          {
              energy = maxEnergy; // Reset energy to max
              grounded = true;
          }
      }
      void OnCollisionExit(Collision col) // When the character stops colliding with something
      {
          if(col.collider.tag == "ground") // If the object has the tag "ground"
          {
              grounded = false;
          }
      }
  }

to the character,when i press play there is another error:Assets/scripts/Volo.cs(24,59): error CS1061: Type UnityEngine.Transform' does not contain a definition forvelocity' and no extension method velocity' of type UnityEngine.Transform'could be found (are you missing a using directive or an assembly reference?)What should i do? I really need it in a few days. thanks in started.