Make mobile navigation menu to be one line

To make mobile navigation menu to be one line, you can use this code to Custom CSS box

div.header-menu-nav-item-content {
    white-space: nowrap;
}

Sometimes this code will make text overflow screen, so you can add text size for it.

div.header-menu-nav-item-content {
    white-space: nowrap;
    font-size: 14px;
}