Complex sentence: When the ban on the Party was lifted in 1943, the first Party Congress was held at Bombayand he was again elected to the Central Committee in the second party Congress held at Calcutta (now called: Kolkata).
Split into simpler sentences: When the ban on the Party was lifted in 1943, the first Party Congress was held at Bombay. He was again elected to the Central Committee in the second party Congress held at Calcutta (now called: Kolkata).