Dear @Grisid
basically:
Button
a div with the class called button
Popup
a div with the class called popup
CSS
.popup {
display: none;
}
.popup.active {
display: block !important;
}
Javascript
jQuery(document).on("click", ".button", function(event) {
jQuery('.popup').toggleClass('active');
});
I did not test it, but that is the way to go!
Best!
Marius