How to remove menu twitching?

Question

css

realtyland.aligan.ru
gyazo.com/b2ba955548f72a71bfdecd9647e35246
Please note that in the APARTMENT OFFERS block, if you click on the photo, the fancibox opens, and then close it, you can see how the menu twitches. As I understand it, because the menu is fixed and the screen width changes when the fancibox opens, but I still don’t understand where it is set in fancybox in css

Answer 1

$(".fb").fancybox({
    openEffect  : 'elastic',
    closeEffect : 'elastic',
    afterShow: function() {
        //$(".nav-menu-fixed").hide();
    },
    afterClose:function() {
        //$(".nav-menu-fixed").show();
    }
});

Try to remove the effects when opening / closing.
I would also replace hide/show with slideUp/slideDown.