Usually, yes. The IRS states that U.S. citizens and resident aliens living abroad generally file and pay in the same way as people living in the United States. Whether a return is required depends on filing status, age and gross income, including income that may later be excluded under the Foreign Earned Income Exclusion.
Start with a complete income inventory: German employment, self-employment, interest, dividends, rental income, investments, pension items and income from any other country. Convert reported amounts to U.S. dollars using a consistent supportable method.