Hi Yasmin, out here on the west coast we don't get a lot of requests for German, so you might want to double check with a German reseller or hopefully they will chime in here but it looks like the only thing available in German right now is the online help as of 2012 sp2.0. I checked where the tutorials and technical references are located and it looks like only english and japanese exist. (C:\Program Files\SolidWorks Corp 2013\SolidWorks Flow Simulation\lang)
Here's the reference I found from the SolidWorks KB:
Question:In what languages is Flow Simulation available?
Visible to Customer:
Answer:For legacy versions, Flow simulation was only available in English and Japanese.
In version 2011 SP3.0, French and German UI and Online help were added.
In version 2012 SP2.0, Simplified Chinese UI and Online Help were made available.