Fade In/out issue about a gameobject

hello friends I have a diffucult issue. If anyone help me it will be appreciated

I have a gameobject as sprite I have a dropdown list -Fade In -Fade out

and I have a button to work

I tred these function for 2 ways but not successfull

1- IENumerator 2-Color.Lerp

1- /////////////

using System.Collections; using System.Collections.Generic; using UnityEngine;

public class Lastfade : MonoBehaviour { SpriteRenderer element; bool selected = true; float ali, veli, f; void Start() { element = GetComponent(); }

 IEnumerator fadein()
 {
     Color c = element.material.color;
     c.a = ali;
     element.material.color = c;

     for (f = 0f; f <= 1; f += 0.05f)
     {
         //Color c = element.material.color;
         c.a = ali;
         element.material.color = c;
         yield return new WaitForSeconds(0.05f);
     }
 }

 IEnumerator fadeout()
 {
     for (f = 1f; f >= -0.05f; f -= 0.05f)
     {
         Color c = element.material.color;
         c.a = veli;
         element.material.color = c;
         yield return new WaitForSeconds(0.05f);
     }
 }

 public void FadeAyar(int val)
 {
     if (val == 0)
     {
         Debug.Log("Please choose option!");
     }
     else if (val == 1)
     {
         selected = true;
         ali = 0f;
     }
     else if (val == 2)
     {
         selected = false;
         veli = f;
     }
     else if (val == 3)
     {
         //Bakılacak
     }

 }

 public void startFadeIn()
 {
     if (selected == true)
     {
         StartCoroutine("fadein");
     }
     else if (selected=false)
     {
         StartCoroutine("fadeout");

     }
 }

}

2- /////////////

using System.Collections; using System.Collections.Generic; using UnityEngine;

public class Fadework : MonoBehaviour { float speed = 1f;

 public Color alphaV0, alphaV1; //from inspector on color tab, alphaV0=  all slider to left, alphaV1= all sliders to right

 Color startColor, endColor;
 float startTime;
 bool selected = false;
 private void Start()
 {
     startTime = Time.time;
 }


 public void FadeOption(int val)
 {
     if (val == 0)
     {
         Debug.Log("Please choose option!");
     }
     else if (val == 1)
     {
         startColor = alphaV0;
         endColor = alphaV1;
     }
     else if (val == 2)
     {
         startColor = alphaV1;
         endColor = alphaV0;
     }
     else if (val == 3)
     {
         //Bakılacak
     }

 }       

 public void GenerateButton()
 {
     selected = true;
     float t = (Time.time - startTime) * speed;
     GetComponent<Renderer>().material.color = Color.Lerp(startColor, endColor, t);

 }    

 private void Update()
 {
     if (selected == true)
     {
         GenerateButton();
     }
 }

}