.drehen{
    transform: rotate(-60deg);
}
.animation_drehen{                
    animation-name: rotateback;
    animation-duration: 2s;
    animation-iteration-count: 1;
    animation-timing-function:ease-in-out;
    animation-fill-mode: forwards;
}
@keyframes rotateback {
    0%  { transform: rotate(-60deg);}
    100%{ transform: rotate(0);}
}