.aufgaben_desc {
  display: flex;
  justify-content: center; /* horizontally centers the images */
  align-items: center; /* vertically centers the images */
  border-radius: 25px;
  background: #f0f0f0;
}

.aufgaben_desc figure img {
    width: 100%;
    padding-left: 5px;
    padding-right: 5px;
}

.aufgaben_desc img {
    width: 30%;
    padding-left: 5px;
    padding-right: 5px;
}

.aufgaben_desc figcaption {
    /* Make the caption a block so it occupies its own line. */
    display: block;
    width: 100%;
    height: 30px;
    padding-top: 7px;
    border-radius: 5px;
    border: 2px solid black;
    font-size: 20px;
    font-weight: 100;
    color: white;
}

.aufgaben_desc .in{
    background-color : green;
}

.aufgaben_desc .out{
    background-color : blue;
}

.aufgaben_desc figure {
    /* To correctly align image, regardless of content height: */
    vertical-align: top;
    display: inline-block;
    /* To horizontally center images and caption */
    text-align: center;
    width: 30%;
    max-width: 100%;
    
}