body {
  background-image: 
    url('../images/fringlabs-logo-transparent.png'), 
    url('../images/bg.jpg');
  background-repeat: no-repeat, no-repeat;
  background-position: left 0px top 70px, center center;   /* <--- 40px nach unten */
  background-attachment: fixed, fixed;
  background-size: 120px auto, cover;
  color: white;
}

header {
  background: rgba(0, 0, 0, 0.7);
  padding: 1rem;
  text-align: center;
}

nav {
  background: rgba(0, 0, 0, 0.8);
  padding: 0.5rem;
  text-align: center;
}

nav a {
  color: white;
  text-decoration: none;
  margin: 0 1rem;
  font-weight: bold;
}

nav a:hover {
  text-decoration: underline;
}

main {
  background: rgba(0, 0, 0, 0.6);  /* <--- 0.6 */
  max-width: 800px;
  margin: 2rem auto;
  padding: 2rem;
  border-radius: 8px;
}

a {
  color: #999;
}
a:hover {
  color: #ccc;
}
.mainmenu ul {
  list-style: none;
  margin: 0;
  padding: 0;
  background: #222;
}

.mainmenu li {
  position: relative;
  display: inline-block;
}

.mainmenu > ul > li > a {
  display: inline-block;
  padding: 0.7em 1.4em;
  color: white;
  text-decoration: none;
  white-space: nowrap;
}

.mainmenu > ul > li:hover {
  background: #444;
}

.submenu {
  display: none;
  position: absolute;
  top: 100%;
  left: 0;
  background: #333;
  min-width: 160px;
  z-index: 10;
}

.mainmenu > ul > li:hover > .submenu,
.mainmenu > ul > li:focus-within > .submenu {
  display: block;
}

.submenu li {
  display: block;
  white-space: nowrap;
}

.submenu li a {
  padding: 0.8em 2em 0.8em 1em;
  display: block;
  color: white;
  text-decoration: none;
  background: none;
}

.submenu li a:hover {
  background: #555;
}