hi guys i have script for movement and everything works fine but i want to add sprinting when W is holded for 5 seconds here is my script.

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

public class tebrawtf : MonoBehaviour
{
public CharacterController controller;

public float speed = 12f;
public float gravity = -19.62f;
public float jumpHeight = 3f;


public Transform groundCheck;
public float groundDistance = 0.4f;
public LayerMask groundMask;

Vector3 velocity;
bool isGrounded;
bool midAirJump;

// Update is called once per frame
void Update()
{
    isGrounded = Physics.CheckSphere(groundCheck.position, groundDistance, groundMask);

    if(isGrounded && velocity.y < 0)
    {
        velocity.y = -2f;
    }

    float x = Input.GetAxis("Horizontal");
    float z = Input.GetAxis("Vertical");

    Vector3 move = transform.right * x + transform.forward * z;

    controller.Move(move * speed * Time.deltaTime);
    if (Input.GetButtonDown("Jump"))
    {
        if (isGrounded)
        {
            velocity.y = Mathf.Sqrt(jumpHeight * -2f * gravity);    //your jumping code
            midAirJump = true;
        }
        else if (midAirJump)
        {
            velocity.y = Mathf.Sqrt(jumpHeight * -2f * gravity);    //your jumping code
            midAirJump = false;
        }
    }

    velocity.y += gravity * Time.deltaTime;

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

}

CODE NOT TESTED

 public float walkSpeed = 12f;
 public float runSpeed = 20f;
 public float gravity = -19.62f;
 public float jumpHeight = 3f;
 
 public Transform groundCheck;
 public float groundDistance = 0.4f;
 public LayerMask groundMask;
 float speed;
 Vector3 velocity;
 bool isGrounded;
 bool midAirJump;
 float runTimer;
 // Update is called once per frame
 void Update()
 {
     isGrounded = Physics.CheckSphere(groundCheck.position, groundDistance, groundMask);
     if(isGrounded && velocity.y < 0)
     {
         velocity.y = -2f;
     }
     float x = Input.GetAxis("Horizontal");
     float z = Input.GetAxis("Vertical");
     
     if(z > 0)
     {
        runTimer += Time.deltaTime;
        if(runTimer > 4)
            speed = runSpeed;
     }
     else
     {
        speed = walkSpeed;
        runTimer = 0;
     }
     
     Vector3 move = transform.right * x * walkSpeed + transform.forward * z * speed;
     controller.Move(move * Time.deltaTime);
     if (Input.GetButtonDown("Jump"))
     {
         if (isGrounded)
         {
             velocity.y = Mathf.Sqrt(jumpHeight * -2f * gravity);    //your jumping code
             midAirJump = true;
         }
         else if (midAirJump)
         {
             velocity.y = Mathf.Sqrt(jumpHeight * -2f * gravity);    //your jumping code
             midAirJump = false;
         }
     }
     velocity.y += gravity * Time.deltaTime;
     controller.Move(velocity * Time.deltaTime);
 }

i tested you code @Hellium and it works bt you it kinda slowed my speed when normal walking but i gave bigger number to speed and now its all good thanks and also thanks to fast responde