Complex sentence: Khan subsequently joined a theatre group called Avantar, where he worked backstage for a year and a half, following which he made his stage debut with a small role in their Gujarati play, "Kesar Bina", at Prithvi Theatre.
Split into simpler sentences: Khan subsequently joined a theatre group called Avantar, where he performed backstage activities for over a year. He made his stage debut with a small role in the company's Gujarati play, "Kesar Bina", at Prithvi Theatre.