body {
font-size: 120%;
font: normal 15px/140% Helvetica, Arial, sans-serif;
<!-- font-family:"Helvetica Neue", Arial, sans-serif;-->
line-height: 1.4;
color: #263238;
background-color: #dddddd;
margin:0.3rem;
padding: 0.8rem;
}
h1 {
font-size:3rem;
font-weight: normal;
text-align: center;
padding: 2rem;margin: 0;
}
h2 {
font-size:2rem;
text-align: center;
margin: 0; padding: 1rem;
color: red;
}
h3 {
  font-size: : 2rem;
  font-weight: normal;
  text-align: center;
  margin: 0;
}
h5 {
  font-size: : 1rem;
  font-weight: normal;
  text-align: left;
  margin: 0;
}
h6 {
  font-size: 0.6rem;
  font-weight: normal;
  text-align: center;
  margin: 0;
}

nav {font: normal 20px/140% Helvetica, Arial, sans-serif; background-color: #bbbbbb; display: flex; line-height: 1.5; }
nav ul {margin: 0; display: flex; list-style: none; flex-wrap: wrap;}
nav a {color: white; text-decoration: none; display: flex; padding: 0.5rem; padding-top: 0.7rem; padding-bottom: 0; margin: 0.3rem;}
nav a.aktuell {font-weight: bold; color:blue; }
footer { background-color: #bbbbbb; color: #555555; padding: 0; margin-top: 0rem; margin-bottom: 0; line-height: 0.9; padding-bottom: 0;}