Complex sentence: In 1987, Braunschweig managed to set a mark even as they were demoted; it became the only team ever to have been relegated with a positive goal differential, with 52 goals for and 47 against.
Split into simpler sentences: In 1987, Braunschweig managed to set a mark even as they were demoted. They are the only team ever to have been relegated with a positive goal differential: 52 goals for and 47 against.