JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Dropdown menu</title>
  </head>
  <body>
    <nav>
      <div class="nav">
        <a href="#">Главная</a>
      </div>
      <div class="dropdown">
        <button class="dropdown">Меню 1</button>
        <div class="dropdown-content">
          <a href="#">Подменю 1.1</a>
          <a href="#">Подменю 1.2</a>
        </div>
      </div>
      <div class="dropdown">
        <button class="dropdown">Меню 2</button>
        <div class="dropdown-content">
          <a href="#">Подменю 2.1</a>
          <a href="#">Подменю 2.2</a>
        </div>
      </div>
      <div class="nav">
        <a href="#">Меню 3</a>
      </div>
      <div class="dropdown">
        <button class="dropdown">Меню 4</button>
        <div class="dropdown-content">
          <a href="#">Подменю 4.1</a>
          <a href="#">Подменю 4.2</a>
          <a href="#">Подменю 4.3</a>
        </div>
      </div>
      <div class="nav">
        <a href="#">Справка</a>
      </div>
    </nav>
  </body>
</html>

CSS

body {
  font-family: sans-serif;
}
nav {
  color: black;
  width: 100%;
  text-align: center;
  border-radius: 8px;
}
div.nav, div.dropdown {
  display: inline-block;
  vertical-align: top;
  position: relative;
  width: 16%;
  text-align: center;
  font-weight: bold;
}
div.dropdown-content {
  position: absolute;
  display: none;
  width: 100%;
  overflow: auto;
  text-align: left;
  font-size: 90%;
}
div.dropdown:hover div.dropdown-content {
  display: block;
}
div.dropdown-content a, div.nav a {
  display: block;
  background: lightgrey;
  color: black;
  text-decoration: none;
  padding: 0.3em 0;
}
div.dropdown-content a {
  font-weight: normal;
}
div.dropdown-content a:hover, div.nav a:hover {
  background: darkseagreen;
  border-radius: 4px;
}
button.dropdown {
  background: lightgrey;
  color: black;
  width: 100%;
  height: 100%;
  border: 0px;
  font-size: 100%;
  font-weight: bold;
  padding: 0.4em;
}
button.dropdown:hover {
  background: darkseagreen;
  border-radius: 4px;
}