Contact Import German Date Format support?
Maybe, the easiest way is, to open the csv in Excel (or LibreCalc) and do some magic with formulas?

Something like 

=SUBSTITUTE(C9;".";"/")

Or even much easier: Open the file in Excel (or LibreCalc) and do some search and replace in the column?

That's the way I would do it, if the file isn't to big for Excel and it isn't a work I had to do every day.