<header>
  <a href="" class="logo">logo</a>
  <nav>
    <ul>
      <li><a href="">nav01</a></li>
      <li><a href="">nav02</a></li>
      <li><a href="">nav03</a></li>
      <li><a href="">nav04</a></li>
    </ul>
  </nav>
</header>

header {
  display: flex;
  justify-content: space-between;
  align-items: center;
}
header .logo {
  background: #eee;
  padding: 10px 20px;
}
nav ul {
  margin: 0;
  display: flex;
}
nav li {
  margin: 0 10px;
  list-style-type: none;
}