Для начала скачайте отсюда https://github.com/Unity-Technologies/NavMeshComponents расширенные компоненты для Nav Mesh

Модели девочки и зомби:

Не забудьте на девочку и на зомби добавить компонент NavMeshAgent

Скрипты для ИИ.

//ZombieController.cs
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.AI;
[RequireComponent(typeof(NavMeshAgent))]
public class ZombieController : MonoBehaviour
{
    private GameObject target;
    private NavMeshAgent agent;
    private CharacterController controller;

    void Awake()
    {
        target = GameObject.Find("/Player");
        agent = GetComponent<NavMeshAgent>();
        StartCoroutine(AttackPlayer());
    }

    void Update()
    {
        
    }

    IEnumerator AttackPlayer()
    {
        while (true)
        {
            agent.SetDestination(target.transform.position);
            yield return new WaitForSeconds(0.5f);
        }
    }

}

//PlayerController.cs
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.AI;
[RequireComponent(typeof(NavMeshAgent))]
public class PlayerController : MonoBehaviour
{
    private NavMeshAgent agent;
    private CharacterController controller;

    void Awake()
    {
        agent = GetComponent<NavMeshAgent>();
    }

    void Update()
    {
        if (Input.GetMouseButtonDown(0))
        {
            RaycastHit hit;

            if (Physics.Raycast(Camera.main.ScreenPointToRay(Input.mousePosition), out hit, 100))
            {
                agent.destination = hit.point;
            }
        }
    }
}

//CameraFollower.cs
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class CameraFollower : MonoBehaviour
{

    private Transform player;
    public Vector3 offset = new Vector3(0, 2, -10);

    void Awake()
    {
        player = GameObject.Find("/Player").transform;
    }

    void Update()
    {
        
    }

    private void LateUpdate()
    {
        transform.position = player.position + offset;
    }
}

Все скрипты архивом.

В ИТОГЕ ДОЛЖНО У ВАС ВЫЙТИ