Change Sprite/Image of Button by clicking another buttons

I am novice in unity, I tried to use this code from another post but it only worked for one image, so I got to click in one button and change the image, but if I clicked another button I changed the same image.

 public Image UIImagen;
 
 public void Start(){
 UIImagen = GameObject.Fin("Image").GetComponent<Image>();
 }
 
 public void Update() {
 
 If (Input.MouseDown(0)) {
 UIImagen.sprite  = Resources.Load<Sprite>("Sprite/Image1"); // 
 }
 
 }

I added this script to all the buttons but changing Sprite/ImageX ... it did not work.

Also I tried to do it with gameObjects actives (true/false) but I did not work :(

  gameObject.GetComponent().enabled = false;

At the beggining I thought It was a low level task but finally I could not get it :( Please find attached the image in order to clarify:

[1]: /storage/temp/100321-sin-titulo.png

Some piece of advice would be appreciate, thank you in advance!