nav {
  position: sticky;
  top: 10px;
}
footer {
  position: sticky;
  bottom: 10px;
  text-align: left;
}
p {
  position: fixed;
}
h1 {
  position: absolute;
}

.back-to-top {
  position: fixed;  
  bottom: 20px;     
  right: 20px;      
  z-index: 1000;    
}

.back-to-top:hover {
  background-color: #555;
}