It turns out that the concert I was told about in Berlin on 05 July at "Berlin Rock Festival" takes place on 04 July and at the "Gropius Passagen", a shopping centre in Berlin, in reality. No further information found. And the people from the "Gropius Passagen" only wrote back to say that they confirm the event (apparently on the afternoon of Saturday, the 04 th of July 2009 sometime) and wil lannounce it on their website soon.
Well... "soon" would be nice, as it's only three more weeks to go...