[Fixed]-Model shows last for loop image

That’s because you have data-target="#myModal" and below you have <div class="modal fade" id="myModal"... for each image.

So, each div has the same id. In order to work, you should make that unique for each image. Like this:

data-target="#myModal-{{ forloop.counter }}">  <!--  this will become #myModal-1 #myModal-2 #myModal-3 etc -->

and

<div class="modal fade" id="myModal-{{ forloop.counter }}" ...  <!--  this will become myModal-1 myModal-2 myModal-3 etc -->