Complex sentence: The Goethe-Institut New York doesn't offer language courses at its Spring Street location, but since 1980, the official partner for language courses has been Deutsches Haus at New York University.
Split into simpler sentences: The Goethe-Institut New York does not offer language courses at its Spring Street location. However, since 1980, the official partner for language courses has been Deutsches Haus at New York University.