How could i create a fill bar which increase with a key press or decrease in function of time?

Hello! Im trying to create a fillbar which increase with a key press. The bar already increases, but i can't make the increase.

Here is my code:

 //Bar
     public Image bar1;
     public bool encendido;
     public float Tiempo = 30.0f;
  
 void Update () {
 if (encendido == true)
         {
             bar1.fillAmount -= 1.0f / Tiempo * Time.deltaTime;
  
         }
  
  
         if (Input.GetKeyDown("F")) {
             bar1.fillAmount += 2.0f;
             bar1.fillAmount = barraroja.fillAmount;
  
         }