Complex sentence: He served in several high-ranked positions in the 1990s--the Minister of Internal Affairs of Armenia from 1992 to 1996 and the Mayor of Yerevan from 1996 to 1998.
Split into simpler sentences: He served in several high-ranked positions in the 1990s. He was the Minister of Internal Affairs of Armenia from 1992 to 1996 and the Mayor of Yerevan from 1996 to 1998.