Stopped

Yesterday I stopped at this sign (e.g. 290 StVO: restricted stop ban for a zone) to get a short answer to the mobile phone. Then the police arrived and I said I shouldn’t stand here and that’s 15 €. I paid the same as well. But as far as I know I can stand here for 3 minutes or I’m wrong. I went to the station afterwards and told the police officer that I can’t even hold (<3 min) for a short time. Am I or the Polimannnzist in the Right?