I am trying to make a first person controller but I can't make ta player jump. Can I solve this problem without importing assets?

//Here is how my code looks like

using System.Collections; using System.Collections.Generic; using UnityEngine;

public class ControlScript : MonoBehaviour { [SerializeField] Transform firstPersonCamera = null;

 bool isSprinting => canSprint && Input.GetKey(sprintKey);

 [Header("Functional Variables")]
 [SerializeField] private bool lockCursor = true;
 [SerializeField] private bool canSprint = true;

 [Header("Control Variables")]
 [SerializeField] private KeyCode sprintKey = KeyCode.LeftShift;

 [Header("Movement Variables")]
 [SerializeField] private float mouseSensitivity = 3.5f;
 [SerializeField] private float movementSpeed = 6.0f;
 [SerializeField] private float sprintSpeed = 10.0f;

 [Header("Smoothing Variables")]
 [SerializeField] private float moveSmoothTime = 0.3f;
 [SerializeField] private float mouseSmoothTime = 0.03f;

 [Header("Jumping Variables")]
 [SerializeField] private float gravity = 13.0f;

 float upwardForce = 0.0f;
 float cameraPitch = 0.0f;
 CharacterController controller = null;

 Vector2 currentMoveInput = Vector2.zero;
 Vector2 currentMoveInputVelocity = Vector2.zero;

 Vector2 currentMouseInput = Vector2.zero;
 Vector2 currentMouseInputVelocity = Vector2.zero;
 
 // Start is called before the first frame update
 void Start()
 {
     controller = GetComponent<CharacterController>();
     if (lockCursor) 
     {
         Cursor.lockState = CursorLockMode.Locked;
         Cursor.visible = false;
     }
 }

 // Update is called once per frame
 void Update()
 {
     UpdateMouseLook();
     UpdateMovement();
 }

 void UpdateMouseLook()
 {
     Vector2 mouseInput = new Vector2 (Input.GetAxis("Mouse X"), Input.GetAxis("Mouse Y")) * mouseSensitivity;

     currentMouseInput = Vector2.SmoothDamp(currentMouseInput, mouseInput, ref currentMouseInputVelocity, mouseSmoothTime);

     cameraPitch -= currentMouseInput.y * mouseSensitivity;

     cameraPitch = Mathf.Clamp(cameraPitch, -90f, 90f);

     firstPersonCamera.localEulerAngles = Vector3.right * cameraPitch;

     transform.Rotate(Vector3.up * mouseInput.x * mouseSensitivity);
 }

 void UpdateMovement()
 {

     Vector2 moveInput = new Vector2 ( Input.GetAxisRaw("Horizontal"), Input.GetAxisRaw("Vertical"));
     moveInput.Normalize();

     currentMoveInput = Vector2.SmoothDamp(currentMoveInput, moveInput, ref currentMoveInputVelocity, moveSmoothTime);

     if (controller.isGrounded)
     {
         upwardForce = 0f;
     }
     upwardForce -= gravity * Time.deltaTime;

     Vector3 move = (transform.forward * currentMoveInput.y + transform.right * currentMoveInput.x) * (isSprinting ? sprintSpeed : movementSpeed) + Vector3.up * upwardForce;

     controller.Move(move * Time.deltaTime);
 }

}