Complex sentence: He started his career with one of the world's leading agencies, Ogilvy & Mather, in Delhi, and over 10 years, became a creative star and rose to be Executive Creative Director of the flagship Mumbai office.
Split into simpler sentences: He started his career with one of the world's leading agencies, Ogilvy & Mather, in Delhi. Over 10 years, he became a creative star and rose to be executive creative director of the flagship Mumbai office.