According to VW, the damage is irreparable and the dash would be replaced because there was a plasticizer migration. The manufacturer of the holder also does not go as far as we one on my e-mail :(
Since so be careful and mount the tests previously on a hidden place, for it is a great pity if a holder for approx 17 caused damage of more than 1000.
Addendum:
The manufacturer has since contacted me and offered me to remedy this by a professional.
Addendum 2:
The manufacturer has refunded me the cost of the "almost" complete removal. However, the impression is still visible under certain lighting conditions.