#praxis {
    display: flex;
    flex-direction: column;
  }
  
  .praxis-head {
    text-align: center;
  }
  
  .praxis-galerie {
    display: flex;
    flex-flow: row wrap;
    justify-content: space-between;
    align-items: stretch;
  }
  
  .box {
    position:relative;
    margin:10px;
    height:50px;
  }
  
  .size1{
      display: inline-flex;
      width: 45%;
      height: auto;
  }

  /* .size2{flex: 2 200px}
  .size3{flex: 3 300px}
  .size4{flex: 4 400px} */
  
  .color1{background:#2ecc71}
  .color2{background:#3498db}
  .color3{background:#f1c40f}
  .color4{background:#e74c3c}