C# Enemy AI, when player is not visible i want the Enemy to chase the player for a few more seconds and then stop.

The enemy is sitting and if a player interacts with it it chases the player and if it cannot find the player in a few seconds the enemy will go sit again, the script works but i can't make the AI wait for a few seconds. any tips?

public class SittingEnemyAI : MonoBehaviour {

      [Header("Transforms")]
      public Transform ChairPoint;
      public Transform player;
      public Transform Front;
  
      [Header("Sight Range")]
      public float Range;
  
      [HideInInspector]
      public Animator anim;
      [HideInInspector]
      private NavMeshAgent agent;
  
      [HideInInspector]
      public bool Patrolling;
      private bool lost;
  
      void Awake () 
      {
          agent = GetComponent<NavMeshAgent>();
          anim = GetComponentInChildren<Animator> ();
          Patrolling = true;
      }
  
      void Update () 
      {
          if (Patrolling == true) 
          {
              lost = false;
              Lost ();
          }
          if (lost == true) 
          {
              StartCoroutine (StillLooking ());
          }
  
          //Debug.DrawRay (Front.position, Front.forward * Range);
          RaycastHit hit;
          Ray View = new Ray (Front.position, Front.forward);
  
          if (Physics.Raycast (View, out hit, Range)) 
          {
              if (hit.collider.tag == "Player") 
              {
                  Chasing ();
                  StopCoroutine (StillLooking ());
              } 
              else
              {
                  if (Patrolling == false) 
                  {
                      lost = true;
                  }
              }
          } 
          else 
          {
              if (Patrolling == false) 
              {
                  lost = true;
              }
          }
  
          if (anim.GetCurrentAnimatorStateInfo (0).IsName ("sit_to_stand")) 
          {
              anim.SetBool ("StandUp", false);
          }
          if (anim.GetCurrentAnimatorStateInfo (0).IsName ("Running")) 
          {
              Chasing ();
          }
          if (anim.GetCurrentAnimatorStateInfo (0).IsName ("Walk")) 
          {
              agent.destination = ChairPoint.position;
              Patrolling = true;
          }
  
          if (anim.GetCurrentAnimatorStateInfo (0).IsName ("looking_around")) 
          {
              agent.destination = this.transform.position;
              anim.SetBool ("StandUp", false);
          }
  
          if (anim.GetCurrentAnimatorStateInfo (0).IsName ("Typing")) 
          {
              transform.rotation = ChairPoint.transform.rotation;
          }
      }
  
      public void Chasing()
      {
          anim.SetBool ("Chase", true);
          agent.destination = player.position;
  
          agent.speed = 3.0f;
          agent.angularSpeed = 360.0f;
  
          Vector3 lookAtPosition = player.position;
          lookAtPosition.y = transform.position.y;
          transform.LookAt (lookAtPosition);
          anim.SetBool ("Sit", false);
          Patrolling = false;
      }
  
      void Lost()
      {
          anim.SetBool ("Chase", false);
          agent.speed = 0.5f;
          Patrolling = true;
      }
  
      void OnTriggerEnter(Collider collider)
      {
          if (collider.tag == "EnemySit") 
          {
              anim.SetBool ("Sit", true);
          }
      }
  
      IEnumerator StillLooking()
      {
          Chasing ();
          yield return new WaitForSeconds (3);
          Lost ();
          lost = false;
          Patrolling = true;
      }
  }