#button-to-top {
   
    position: fixed;
    bottom: 20px;
    right: 20px;
    z-index: 99;
    background-color: #007bff;
    color: #fff;
    border: none;
    border-radius: 50%;
    cursor: pointer;
    padding: 10px 15px;
    transition: all .5s ease-in-out;
}

#button-to-top::after {
   
    font-family: FontAwesome;
    font-weight: normal;
    font-style: normal;
    font-size: 25px;
    line-height: 40px;
    margin-left: 7px;
    color: #fff;
  }

  #button-to-top:hover {
    cursor: pointer;
    background-color: #333;
  }
  #button-to-top:active {
    background-color: #555;
  }
  #button-to-top.show {
    opacity: 1;
    visibility: visible;
  }