header {
    position: sticky;
    top: 0;
    z-index: 1000;
}

#navbar-menu {
    transition-property: max-height, opacity;
    transition-timing-function: cubic-bezier(0.4, 0, 0.2, 1);
    transition-duration: 300ms;
}

#nav-menu1 {
    transition-property: max-height, opacity;
    transition-timing-function: cubic-bezier(0.4, 0, 0.2, 1);
    transition-duration: 300ms;
}