Question about Samsung UE55CU7170

Hi, does anyone know how to activate TimeShift / Recording on the Samsung SmartTV CU7170? I have added an USB Stick with 200 GB Capacity, I can see the USB Stick in the Devices list and access Video Files stored on the Stick, but I cannot Activate Time Shift or Record TV Shows, it says "nicht verfügbar" (i.e. "not available") when I chose the option via remote.