Complex sentence: He joined Drug Enforcement Administration (DEA) in mid- 1980s and started working in Miami, where he stayed for four years, before being transferred to Bogotá, Colombia, where he played an important role in the killing of Escobar.
Split into simpler sentences: He joined Drug Enforcement Administration (DEA) in mid- 1980s and started working in Miami. He was later transferred to Bogotá, Colombia, where he played an important role in the killing of Escobar.