.masterclass{
    position: relative;
    height: 33vw;
    width: 100%;
    background: url(../image/Florent\ 3.jpg) center;
    background-size: cover;
    padding-top: 30px;
    padding-bottom: 30px;
    display: inline-block;
    text-align: center;
}

@media only screen and (max-width: 720px) {
    .masterclass{
        height: 70vw;
    }

}