How I can attach an image or animation on the uiImage fill amount?

I have a burning fuse, i am burning the fuse using the UIImage. fill amount

i want at the end of the fill amount to attach a uiimage animation that is a burning fire.

how i can do that? With my following code start synchronised but very soon gets desynchronised the fire movement and the fill amount.

What i am missing? any suggestions?

     //----------------------------------------------------------------------------
     // Unity Lifecycle:
     //----------------------------------------------------------------------------
 
     void Update()
     {
         if(start)
         {
             timer += Time.deltaTime * increasedSpeed;
             burnSpeed = (Time.deltaTime * increasedSpeed);
 
             if(timer < totalBurnTime)
             {
                 fuse.fillAmount = timer / totalBurnTime;
             
                 fireRectTransform.anchoredPosition = Vector2.Lerp(fireRectTransform.anchoredPosition,burnPosition,burnSpeed / totalBurnTime);
             }
             else 
             {
                 Explode();
             }
         }
     }