Complex sentence: The 6 ducal councilors, one for each District of the city, remained in office for 8 months, they were renewed twice and three at the time and could not be re-elected before two years had passed.
Split into simpler sentences: The 6 ducal councilors, one for each District of the city, remained in office for 8 months. Terms were renewed twice and three at the time and could not be re-elected before two years had passed.