Hey Jasper I got something similar to this website, here are the steps:
First add this element to your Before Footer hook. (Appearence -> GP Hooks)
<div class="unfold"></div>
After this just add this css:
body {
position: relative;
}
#page {
z-index: 1;
}
.unfold {
/* This unit must match the full size of your footer */
height: 429px;
}
.site-footer {
bottom: 0;
position: fixed;
width: 100%;
z-index: -1;
}
I suggest you to follow this tutorial made by Tom for addind custom css: https://generatepress.com/knowledgebase/adding-css/
Hope I’ve helped. 🙂