body{
    margin: 0;
    min-height: 100vh;
    overflow : hidden; overflow-y : scroll;
    
}
.contenedor{
    width: 100%;
    margin: auto;
}

#galeria{
    width: 3100px;
    height: 100px;
    background-image: url(galeria.png);
    background-size: 100% 100%;
    animation: galeria 20s infinite linear;
}

@keyframes galeria{
    to
    {
      background-position: 2000px;  
    }
}