Read the quoted line again: El-Khalid is a German citizen. German courts have overall jurisdiction for all crimes committed by or against German citizens worldwide. For instance, if I kill a US citizen in the US, and I can make it back to Germany, I won´t be extradited - because I´d get a "lifelong" imprisonment by the German courts.
Question: How is it a terrorist who assisted in killing thousands of people in the US gets 15 years in Germany. Which divides out as only 1.8 days per victim. Then you say, if you committed a murder in the US you would get life? Would not you also get 1.8 days?
Kind of a 'Deutchland uber alles' thing right?