Complex sentence: However, Borelli's old-style management did not allow the club to properly handle the emergent football business during the 1980s and by the early 1990s PSG was in serious financial trouble with a debt of 50 million francs.
Split into simpler sentences: However, Borelli's old-style management didn't handle properly the emergent football business during the 1980s. Thus, by the early 1990s, PSG was in serious financial trouble with a debt of 50 million francs.