@media(max-width:991px) {
    .navbar-collapse.collapse .navbar-nav {
        position: fixed;
        z-index: 109;
        left: -100%;
        background-color: #fff;
        width: 100%;
        transition: all 1s;
    }
    .navbar-collapse.collapse.show .navbar-nav {
        left: 0;
        transition: all 1s;
    }
    
}