PLEASE HELP ME!!!!! error CS1525

giving this error in script! talking about that private does not exist. this is the line of this error:

private void SetFeedBackAlpha(float alpha){ Color currentAlpha = feedBackSlender.material.color; currentAlpha.a = alpha;

     feedBackSlender.material.color = currentAlpha;

private one at the beginning are talking about that does not exist, and alpha within the parenthesis also does not exist

Complete Script:

using UnityEngine; using System.Collections;

public class Lanterna : MonoBehaviour {

 public Light spotLightFL;
 public Animation playerAnimation;
 public float speedRun;
 
 private Ray rayToInteract;
 private RaycastHit hitInteract;
 public float rangeInteract;
 public Renderer feedBackSlender;
 
 public float scare = 0;
 public float recoverScare;
 
 // Use this for initialization
 void Start () {
     
 }
 
 // Update is called once per frame
 void Update () {
     
     if(Input.GetMouseButtonDown(1) || Input.GetKeyDown(KeyCode.F)){
         spotLightFL.enabled = !spotLightFL.enabled;
     }
     
     if(Input.GetAxis("Horizontal") != 0 || Input.GetAxis("Vertical") != 0){
         playerAnimation.CrossFade(playerAnimation.clip.name);
     }
     else{
         playerAnimation.Stop();
     }
     
     if(Input.GetKey(KeyCode.LeftShift))
         GetComponent<CharacterMotor>().inputMoveDirection *= speedRun;
     
     if(Input.GetMouseButtonDown(0)){
          rayToInteract = Camera.main.ScreenPointToRay(new Vector3(Screen.width/2, Screen.height/2, 0));
         
          if(Physics.Raycast(rayToInteract, out hitInteract, rangeInteract)){
             if(hitInteract.collider.tag == "InteractObject"){
                 hitInteract.collider.GetComponent<ObjetoColetavel>().Interact();
             }
         }
     }
     
     if(scare > 0){
         scare -= recoverScare;
         if(scare < 0)
             scare = 0;
     }
     
     SetFeedBackAlpha(scare);
     
     if(scare >= 1){
         Die();

 }
 
 private void SetFeedBackAlpha(float alpha){ 
          Color currentAlpha = feedBackSlender.material.color;
     currentAlpha.a = alpha;
     
     feedBackSlender.material.color = currentAlpha;
 }
     
     private void Die(){
         Debug.Log("Eu Morri");
     }

}

please help me, I need to finish my horror game!!!!!!!!!!!!!!!