Complex sentence: In 1989-1990, Londonderry mall went through an extensive renovation, transforming the mall from a dark, gloomy, street themed look into to a bright, open and colourful mall.
Split into simpler sentences: In 1989-1990, Londonderry mall went through a total renovation. The renovation changed the mall from a dark, gloomy, street themed mall to a bright, open and colourful mall.