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.

If you look at Unity’s documentation about the Transform class, you will see that there is indeed no velocity property. What you’re most likely looking for would be the Rigidbody or RigidBody2D component. In fact, if you look up in your code a little bit you’ll see the velocity being set there on that very component.