I'm Yoda

Array(
        "Украшения",
        "produkt/decoration/",
        Array(),
        Array(),
        ""
    ),
    Array(
        "Подменю пункт украшения",
        "https://site.ru",
        Array(),
        Array(
            "FROM_IBLOCK" => 1000,
            "IS_PARENT"   => 1,
            "DEPTH_LEVEL" => 1
        ),
        ""
    ),

.left-menu {
     display: none;
}

@media (min-width: 768px) {
     .left-menu {
        display: block;
     }
}