<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
</head>
<body>
  <div style="position:fixed;">
  <div class="menu-wrap">
    <ul class="menu">
      <li class="menu__item">
        <a href="#" class="menu__link">menu-item</a>
      </li>
      <li class="menu__item">
        <a href="#" class="menu__link">menu-item</a>
      </li>
      <li class="menu__item menu__item_menu">
        <a href="#" class="menu__link">menu-item</a>
        <div class="menu-inner">
          <!-- inner menu -->
          <ul class="menu">
            <li class="menu__item">
              <a href="#" class="menu__link">submenu-item</a>
            </li>
            <li class="menu__item">
              <a href="#" class="menu__link">submenu-item</a>
            </li>
            <li class="menu__item">
              <a href="#" class="menu__link">submenu-item</a>
            </li>
          </ul>
        </div>
      </li>
      <li class="menu__item">
        <a href="#" class="menu__link">menu-item</a>
      </li>
      <li class="menu__item menu__item_menu">
        <a href="#" class="menu__link">menu-item</a>
        <div class="menu-inner">
          <!-- inner menu -->
          <ul class="menu">
            <li class="menu__item">
              <a href="#" class="menu__link">submenu-item</a>
            </li>
            <li class="menu__item">
              <a href="#" class="menu__link">submenu-item</a>
            </li>
            <li class="menu__item">
              <a href="#" class="menu__link">submenu-item</a>
            </li>
          </ul>
        </div>
      </li>
      <li class="menu__item">
        <a href="#" class="menu__link">menu-item</a>
      </li>
      <li class="menu__item">
        <a href="#" class="menu__link">menu-item</a>
      </li>
      <li class="menu__item">
        <a href="#" class="menu__link">menu-item</a>
      </li>
    </ul>
  </div>
    </div>
</body>
</html>
* {
  box-sizing: border-box;
}
.menu-wrap {
  max-width: 200px;
}
.menu {
  padding: 0;
  list-style: none;
  width: 200px;
  overflow-y: auto;
  height: 240px;
}
.menu__item {
  position: relative;
}
.menu__item_menu {
  background: #fbcda2
}
.menu__link {
  display: inline-block;
  vertical-align: top;
  width: 100%;
  padding: 10px;
  border: 1px solid #bababa;
  border-top-color: rgba(0,0,0,0);
  
  text-decoration: none;
  color: black;
}
.menu__item:nth-child(1) .menu__link {
  border-top: 1px solid #bababa;
}
.menu-inner {
  position: absolute;
  right: -100%;
  top: 0;
  display: none;
}

.menu__item:hover .menu-inner {
  display: block;
}

External CSS

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External JavaScript

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