Complex sentence: It was in Mumbai, while dining at a restaurant, that he got an offer to audition for an television commercial to be directed by Dibakar Banerjee of "Khosla Ka Ghosla", and the success of that fetched him more commercials.
Split into simpler sentences: It was in Mumbai, while dining at a restaurant, that he got an offer to audition for an television commercial. That commercial, directed by Dibakar Banerjee of "Khosla Ka Ghosla" fame fetched him many more commercials.