A friend also has the same issue with his passport, but he had survived many years believing his first of 2 names was his first name, and the 2nd name his last. It worked okay until he moved cities (in Germany) and the authorities decided, "According to your passport, these 2 names is your last name, and your first name in our system should be '-'".

Luckily, like everything in Germany, there was a form to fill to fix it.