body {
  padding: 0px;
    margin: 0px;
  background-color: black;
  color: goldenrod;
  font-family: Georgia, 'Times New Roman', Times, serif;
}

   <img 
   src="Dévoué.svg" 
   alt="Logo von Devoue">

   
   
   header {
    margin-bottom: 24px;
    margin-top: 24px;

   }
   .mitte {
    display: flex;
    justify-content: center;
    align-items: center;
   }
   @media screen and (min-width: 800px) { 
    #teaser {
      height: 600px;
    }
    
  }

   #teaser {
    width: 100%;
    height: 300px;
    
   }
   #teaser img {
    width: 100%;
    height: 100%;
    object-fit: cover;
   }
   nav {
    position: sticky;
    top: 0px;
    backdrop-filter:blur (8px);



   }
  footer ul, nav ul {
    list-style: none;
    margin: 0;
    padding: 0;
    padding-bottom: 24px;
    padding-top: 24px;
  }
  footer ul li a, nav ul li a {
    font-weight: 500;
    padding: 16px;
  }
  section {
    max-width: 1200px;
    margin-left: auto;
    margin-right: auto;
    padding-left: 16px;
    padding-right: 16px;
    
  }