I opened international roaming in China, so that I could still use the card while I am in Germany. But it is easier and also cheaper to buy a
new SIM-card in Germany. You just need a passport and then buy either
a prepaid card or make a monthly-fee contract. Flat-rate contracts are quite popular here. My contract costs 9,99 Euros per month including
all-net flat and 1 GB data volume.