I get three errors, no idea why..

The errors I get: https://gyazo.com/0eacdb3c2e1cecc014d121aaebcc58c5 Sorry if I'm retarded! :)

using UnityEngine; using System.Collections;

 public class Gun : MonoBehaviour {
 
     public enum FireMode{Auto, Burst, Single};
     public FireMode fireMode;
     
     public Transform muzzle;
     public Projectile projectile;
     public float msBetweenShots = 100;
     public float muzzleVelocity = 35;
     public float burstCount;
 
     public Transform shell;
     public Transform shellEjection;
     Muzzleflash muzzleflash;
     float nextShotTime;
 
     bool triggerReleasedSinceLastShot;
     int shotsRemainingInBurst;
 
     void Start(){
         muzzleflash = GetComponent<Muzzleflash>();
         shotsRemainingInBurst = burstCount;
     }
 
 
      void Shoot(){
 
         if(fireMode == FireMode.Burst){
 
             if(shotsRemainingInBurst == 0){
                 return;
             }
             shotsRemainingInBurst --;
         }
         else if(fireMode = FireMode.Single){
             if(!triggerReleasedSinceLastShot){
                 return;
             }
         }
 
         if (Time.time > nextShotTime) {
             nextShotTime = Time.time + msBetweenShots / 1000;
             Projectile newProjectile = Instantiate (projectile, muzzle.position, muzzle.rotation)as Projectile;
             newProjectile.SetSpeed (muzzleVelocity);
 
             Instantiate(shell, shellEjection.position, shellEjection.rotation);
             muzzleflash.Activate();
         }
     }
 
     public void OnTriggerHold(){
         Shoot ();
         triggerReleasedSinceLastShot = false;
     }
     public void OnTriggerRelease(){
         triggerReleasedSinceLastShot = true;
         shotsRemainingInBurst = burstCount;
 
     }
 }