Complex sentence: He migrated to Kolkatta in 1890, where he started a shoe shop which in 1938 was transformed into the Kohinoor Rubber works, one of the biggest rubber manufacturing concerns of South Asia at the time.
Split into simpler sentences: He migrated to Kolkatta in 1890 where he started a shoe shop which later transformed into Kohinoor Rubber works in 1938. It was one of the biggest rubber manufacturing concerns of South Asia at the time.