body {
    
    background-image:url("../picture/IMG_3143.JPG");
    background-position:center;
    background-size:cover;
}
.sonnenunter{
    background-position:center;
    background-image: url('../picture/sonnenuntergang_schmal.jpg');
    background-size:cover;
    width:100%;
    height: 187px;
}
.jumbotron{
    text-align: center;
    display:block;
}
.jumbotron p{
    color:gray;
}