JSFiddle - React, Tailwind, and code Playground

HTML

<nav>
    <ul class="menu left">
        <li>
            <a href="smartphones.php">Smartphones</a>
        </li>
        <li>
            <a href="tablets.php">Tablets</a>
        </li>
     </ul>
     <ul class="menu right">
        <li>
            <a href="laptops.php">Laptops</a>
        </li>
        <li>
            <a href="desktops.php">Desktops</a>
        </li>
    </ul>
</nav>

CSS

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

nav {
  width: 100%;
  height: auto;
  background: red;
  position: sticky;
  top: 0;
  flex-direction: row !important;
  flex-flow: row nowrap;
  display: flex;
  align-items: center;
  padding: 10px 15px;
}

.menu {
  display: flex;
  list-style: none;
}

.menu li {
  padding: 0 10px;
}

.menu a {
  text-decoration: none;
  color: #fff;
}

nav .left {
  flex-direction: row !important;
}

nav .right {
  margin-left: auto !important;
  flex-direction: row !important;
}