Thank your for asking for clarification.
So let's work on question by question. My first question aks why it is not working to use several sections as a reference. What I mean by that is: as I scroll, I want the current section to be reference container for it's background-image to scroll within (as indicated on line 16 in the example). So rather than using the window object here to use the whole viewport as scroll height for the parallax, I only want to use the height of the current section. This should lead to each section to have its own parallax with its background-image. My goal with this is to contrain the parallax to the height value of the current section. I hope this is more clear now.
