Sticky navigation problem

Hey guys!
So here’s my issue.
I want each section of my website to be sticky, so that they scroll “on top” of each other.
I’ve gotten it to work when scrolling the website, and when clicking the menu to go to each section.
The problem is, once I’m further down the site, if I click on a section that’s “below” the one I’m currently viewing, nothing happens.
This is because the sections underneath are at a lower z-index, right.
So, how to solve this? Do I need to add something to each button to make it so the site “un-scrolls” when I click a menu item?

Here is my site Read-Only: Webflow - OpiPets GRID