<header>
  <nav>
    <a href="#">link 1</a>
    <a href="#">link 2</a>
    <a href="#">link 3</a>
    <a href="#">long link 4</a>
    <a href="#">link 5</a>
  </nav>
</header>

header {
  width: 600px;
  height: 100px;
  background: radial-gradient(circle, white 0, white 50px, #eee 50px);
}
nav {
  columns: 2;
  column-gap: 100px;
  line-height: 90px;
  height: 100px;
}
nav a {
  font-size: 17px;
  margin: 0 10px;
  white-space: nowrap;
}