Hi Suzan,
There are two ways one can call you from a country and show another country’s code:
1) When one uses a cell phone abroad with a roaming agreement (so if your friend travels to Portugal with his German cell phone, calls made would show a Germany caller ID);
2) There are many VoIP services today that allow users from a certain region/country to register phone numbers belonging to another region/country (for example you could be in Paris but all your friends are in New York – if you register a New York number with a VoIP company all your friends from New York will be able to call you local although you are abroad).
Anyway, this number doesn’t look like a German cell so only the second situation may apply.