How can I create a floating main content with a fixed footer and banner?

[Ab52]

Hi everyone,

I would like to create an animation, where the first image banner and the footer are in a fixed position and the content of the website floating on top revealing the footer. Can someone help me create this? See attachment: https://cdn.shopify.com/videos/c/o/v/6d672764c7b440e6b1d3dbabbe1a9c78.mov