Sticky scrolling HELP!

Hey guys!
I’m building my company’s website and I’ve managed to get the second page (first in the nav menu) to scroll on top of the homepage by just making the home “Fixed” and increasing the Z-index of the second page.
Now I want ALL the sections to scroll on top of each other.

Here is my site Read-Only: LINK
(how to share your site Read-Only link)

Started from scratch, got it.
BUT, since each page is loading on top of one another, if I want to go BACK to menu options that are technically underneath the currently open one, nothing happens.
I have to add some sort of scrolling action to clicks, don’t I.

Anyone got any insight on this?

Someone must have some ideas here… Please?