JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
  <div class="header__list--item open-menu menu-click">Материалы</div>
  <div class="header__list--item open-menu burger-click">Бургер</div>
</div>

 <div class="header__menu">
    Контетн
  </div>

CSS

.container {
  display: flex;
}

.header__list--item {
  padding: 18px 32px;
  background: blue;
  color: #fff;
  text-align: center;
  cursor: pointer;
}

.burger-click {
  padding: 18px 32px;
  background: green;
  color: #fff;
  text-align: center;
  cursor: pointer;
}

.header__menu {
  display: none;
  background: red;
  padding: 52px 18px;
  text-align: center;
  color: #fff;
}

JavaScript

$(function() {
    var $res = $(".header__menu");
    $(".open-menu").on("click", funk);
    $(document).click(function(e) {
        if (!$(e.target).hasClass('open-menu')) funk(false);
    });

    $('.header__menu').on('click', function(e) { e.stopPropagation() });

    function funk(flag) {
			$res.fadeToggle();
    }
});