I need help scripting a shooter

I'm quite new to programming, my teacher asked us to make a shooter with a few limitations, like the enemies can only attack every 5 seconds and such. I'm nearly done, however unity tells me I've made at least 11 mistakes, here's the code of the MainCharacter and Enemy scripts:

using UnityEngine; using System.Collections;

public class Enemy : MonoBehaviour { void Start () {

 }
 public float Velocidad = 10;
 private bool Atacar = false;
 RaycastHit RCH;
 public float DistanciaParaAtacar = 20;
 
 void Update () 
 {
     transform.LookAt(MainCharacter.Jugador.position);
     transform.position += transform.forward * Time.deltaTime * Velocidad;
     if (Vector3.Distance(this.transform.position, MainCharacter.Jugador.position) < DistanciaParaAtacar)
     {
     //Atacar
     }
     transform.LookAt(MainCharacter.Jugador.position);
     if (Physics.Raycast(transform.position,transform.forward, out RCH, Mathf.Infinity))
     {
             if (RCH.collider.gameObject.layer == MainCharacter.LAYER_MAIN_CHARACTER)
         {
             MainCharacter mc = (MainCharacter)RCH.collider.GameObject.GetComponent(typeof(MainCharacter));
             mc.TakeDamage(20);
         }
     }
 }
 public float Vida = 200;
 public void TakeDamage(float damage)
 {
     Vida -= damage;
     if (Vida <= 0)
     {
         GameObject.Destroy(this.gameObject);
     }
 }

}

using UnityEngine; using System.Collections;

public class MainCharacter : MonoBehaviour { public GameObject Jugador; void Start () {

 }
 RaycastHit RCH;
 void Update () 
 {
     if (Input.GetMouseButtonDown(0))
     {
         if (Physics.Raycast(Camera.mainCamera.transform.position, Camera.mainCamera.transform.forward, out RCH, Mathf.Infinity))
         {
             if (RCH.collider.GameObject.layer == LAYER_ENEMY)
             {
                 Enemy e = (Enemy)RCH.collider.GameObject.GetComponent(typeof(Enemy));
                 if (e)
                 { 
                 e.TakeDamage(50);
                 }
             }
         }
     }
 }
 public float Vida = 200;
 public void TakeDamage(float damage)
 {
     Vida -= damage;
     if (Vida <= 0)
     {
     Application.LoadLevel(0);
     }
 }

}

What it should do is allow both my player and my enemies to attack, and when they hit each other using a raycast, they should substract from the var Vida, also when Vida is 0 in enemies, they should be destroyed, and in the player, the whole proyect should reload. However the error log basically says that theres problems with the MainCharacter.Jugador.Transform

If someone could help me I'd be very grateful. Please answer as fast as you can.