.xnav123 {
    display: none;
}

@media only screen and (max-width: 550px) {
    .xnav123 {
        position: fixed;
        z-index: 999;
        bottom: 0;
        width: 100%;
        height: 45px;
        display: flex;
        overflow: hidden;
    }

    .xnav123 div {
        flex: 1;
        text-align: center;
        box-sizing: border-box;
        height: 100%;
        padding: 10px 0;
        text-decoration: none;
        display: block;
    }
}