Animated Background on Scroll

Hello there,
I’m a Webflow noob and struggling with some things.
I’d love to make a Line Background animation, that loads on scroll.
Flux academy is explaining one step, but not actually on a Fullpage, like the example he actually shows. I’d love to have a line animated on scroll over the whole page (Design example):

The other problem I have is with the image-text divided slider I created. I struggled to make it responsive, so I created several for each device( not for mobile horizontal - also struggling).
But on the mobile size the arrows are completly out of place (they’re on top of the page).
I want to have them on the image, and only showing on hover. Once it worked, but somehow something changed and everything is messed up.
Here’s the preview:

Thank you so much for helping me getting better.

Here is my public share link: LINK
(how to access public share link)

Here’s the Flux Tutorial: