<header>
  <img src="https://picsum.photos/2000/150" width="300" height="150">
</header>
<nav class="menu">
  <button class="button" hidden onclick="toggle()"><img src="images/list.png"></img></button>
  <ul class="menu_list">
    <li><a href="#">Home</a></li>
    <li><a href="#">About me</a></li>
    <li><a href="#">Projects</a></li>
    <li><a href="#">Blog</a></li>
    <li><a href="#">Contact</a></li>
  </ul>
</nav>

html {
  box-sizing: border-box;
}
*,
*:before,
*:after {
  box-sizing: inherit;
}

body {
  font-family: Verdana;
  margin: 0;
}
input,
select,
textarea,
button {
  font-family: inherit;
}

header img {
  display: block;
  object-fit: cover;
  width: 100%;
  height: 150px;
}

.menu {
  display: flex;
}
ul.menu_list {
  list-style-type: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex: 1 0 100%;
  background: red;
}
ul.menu_list li {
  flex: 1 0 0;
}

ul.menu_list a {
  background-color: #353839;
  color: white;
  display: block;
  white-space: nowrap;
  padding: 15px 10px;
  text-align: center;
  text-decoration: none;
  border: 1px solid #555d50;
  font-size: 1rem;
}
ul.menu_list a:hover {
  background-color: #006400;
}