Complex sentence: Pratek Man went to Lhasa for the first time in 1939 to join his family business house Chhusingsyar, one of the largest traders in Tibet at the time with branches in Gyantse and Phari besides Ladakh and Kolkata in India.
Split into simpler sentences: Pratek Man went to Lhasa for the first time in 1939 to join his family business house Chhusingsyar, one of the largest traders in Tibet at the time. The firm maintained branches in Gyantse and Phari besides Ladakh and Kolkata in India.