How to fix the footer to the bottom of the screen

I’ve recently created my first Homepage (garageeden.at) with WordPress using Elementor, and have a small issue with the footer (created with the header footer plugin for elementor). Currently it just follows after the content, so on pages with little content it sits in the middle of the page, with blank space under it.
I saw the suggestion of just adding

.site-footer{
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;   
}

but if i do that using the custom css plugin it doesn’t change anything