Complex sentence: The first steps of the formation of the city happened at the second half of the 19th century (1873), which formation came as result of the trade development-which comprises the tertiary sector of the economy.
Split into simpler sentences: The first steps of the formation of the city happened at the second half of the 19th century (1873). Due to the formation, it resulted in the trade development-which comprises the tertiary sector of the economy.