问导航栏在我的页面的某些部分不可见

EN

body {
  height: 100%;
  overflow: auto;
  margin: 0;
  padding: 0;
  line-height: 1.5;
  background-color: white;
  font-family: "Trebuchet MS", Helvetica, sans-serif;
}

.container {
  width: 80%;
  margin: 0 auto;
}

header {
  position: fixed;
  background: #f4f4f4;
  width: 100%;
  height: 15%;
  /*	padding: 0px 30px;*/
  box-sizing: border-box;
}

.name {
  float: left;
  width: 180px;
  padding-right: 150px;
}

nav {
  width: 100%;
  height: 50px;
  top: 0;
  padding: 15px 0px;
  color: black;
  text-decoration: none;
}

nav ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
}

nav li {
  display: inline-block;
  margin-left: 10px;
  margin-top: 0px;
  position: relative;
  padding: 20px;
}

nav ul li a {
  color: black;
  text-decoration: none;
  text-transform: uppercase;
  font-family: "Trebuchet MS", Helvetica, sans-serif;
  transition: .4s;
}

<header>
  <nav>
    <div class="container">
      <div class="name">
        <img src="logoimg.png> </img>
       </div>
        <ul>
          <li><a href=" # " class="sec1 "> Home</a> </li>
          <li><a href="# " class="sec2 "> Who we are</a> </li>
          <li><a href="# " class="sec3 "> What we do</a> </li>
          <li><a href="# " class="sec4 "> Our projects</a> </li>
          <li><a href="# " class="sec5 "> Contact us</a> </li>
        </ul>
    </nav>
</header>