Advanced animation

Hi all, I need some help; I have created a section animation, I have got the general idea of the animation done, but I still need to fine-tune it. But I wanted to ask here if anyone has a better method to do the animation I am trying.

Is there something I am missing? I have attempted various methods, such as just using position sticking and having the sections scroll over each other, but it never quite worked. Anyways, I hope someone out there has an idea.

BTW - It is the page called ers-section

Here is my site Read-Only: [LINK][Read-only]

Here is the published page : ers-section