Hi Jochen,
The HRS construction is a more durable and robust construction, often used in our many schools and centres. It does not have a sandwich layer, so of course it will feel a little softer than a board with a PVC deck. But therefore it has a more durable outer skin for knocks and daily use. The area between the straps where you are changing feet will obviously get more use than other areas on the board, keep an eye on it and if it becomes noticebly worse, then contact the dealer where you bought it - just note, it's a composite product, so every time you push it in with pressure, you are wearing down the stiffness of the laminate - it's not a plastic skin which can then reform to it's original shape.