Complex sentence: In recent years, a move within the city to have Seongnam governed as a gwangyeoksi capable of governing itself has arisen, partly due to Seongnam's growing population and changes in its main function as a city for residents whose workplaces are in Seoul.
Split into simpler sentences: In recent years, a movement to have Seongnam designated a gwangyeoksi capable of governing itself has arisen. This is due in part to Seongnam's growing population and changes in its main function as a city for residents whose workplaces are in Seoul.