Enemy behavior help

So my enemy behavior is working correctly, but my problem is the enemy doesn't have collision or gravity. I have tried adding colliders and rigidbody physics to the enemy, but no matter what she still doesn't have gravity or collision. I have also tried using SimpleMove instead of transform but with that, the enemy just stayed in place.

I can collide with her with the script disabled.

Here is my script:

 using UnityEngine;
 using System.Collections;
  
  
  
 public class EnemyBehavior : MonoBehaviour
 {
     public enum EnemyState{IDLE = 0, WALK = 1, RUN = 2, ATTACK = 3, KILL = 4};
     public AnimationClip enemyIdle;//setting animations
     public AnimationClip enemyWalk;//walking
     public AnimationClip enemyRun;//running/chasing
     public AnimationClip enemyAttack;//attacking player
     public AnimationClip enemyKill;//killing player
  
     public Transform Player;//adds the player to the script
  
     private int Stopped = 0;
     public int WalkingSpeed = 1;//sets the normal walking speed
     public int RunningSpeed = 5;//sets the running (chase player) speed
     public int DefaultRunningSpeed = 5;
     public int MaxDist= 8;//maximum distance the player can be before enemy stops chasing the player
     public int MinDist= 1;//how close the player can be to enemy for enemy to start chasing player
     public EnemyState currentState;
  
     private bool PlayerDetected;
  
     void Update()
     {
        if(Vector3.Distance(transform.position,Player.position) <= MaxDist)//if that object has the tag "Player"
        {
          PlayerDetected = true;
          if (PlayerDetected)
          {
           print ("Player Detected.");
           transform.LookAt(Player);//Looks at the player
           currentState = EnemyState.RUN;
             transform.position += transform.forward*RunningSpeed*Time.deltaTime;//follows the player
          }
        }else if(Vector3.Distance(transform.position,Player.position) > MaxDist)
        {
          RoamAround ();
        }
        if (Vector3.Distance (transform.position,Player.position) < MinDist)
        {
          currentState = EnemyState.ATTACK;
          Attack ();
  
        }
  
        if (currentState == EnemyState.IDLE)
        {
          //print ("The enemy is idle.");
          animation.CrossFade (enemyIdle.name);
        }
        else if (currentState == EnemyState.WALK)
        {
          print ("The enemy is walking.");
          animation.CrossFade (enemyWalk.name);
        }
        else if (currentState == EnemyState.RUN)
        {
          print ("The enemy is running.");
          print ("Distance: " + Vector3.Distance(transform.position,Player.position));
          animation.CrossFade (enemyRun.name);
          RunningSpeed = DefaultRunningSpeed;
        }
        else if (currentState == EnemyState.ATTACK)
        {
          print ("The enemy is attacking.");
          animation.CrossFade (enemyAttack.name);
          RunningSpeed = Stopped;
        }
        else if (currentState == EnemyState.KILL)
        {;
          print ("The enemy is killing.");
          animation.CrossFade (enemyKill.name);
        }
  
     }
     void RoamAround()
     {
        currentState = EnemyState.IDLE;//Add other RoamAround stuff here
     }
     public void Attack()
     {
        //Add attacking stuff here
        //Application.LoadLevel ("GameOver");
     }
 }

What can I do to this script to fix this problem?