German exports slumped by 5.8 percent in August, their biggest fall since the height of the global financial crisis in January 2009, in yet another sign that Europe’s largest economy is faltering amid broader euro zone weakness and crises abroad. The Federal Statistics Office said late-falling summer vacations in some German states had contributed to the fall in both exports and imports, but the figures still painted a gloomy picture for Germany following steep drops in industrial orders and output data earlier in the week.