Complex sentence: He kept working at the plant after the war, in both managerial and Communist Party organizing positions; he was taking evening classes at the Kuybyshev Aviation Institute, finally earning his engineering degree in 1954.
Split into simpler sentences: He kept working at the plant after the war, in both managerial and Communist Party organizing positions. At the same time he was taking evening classes at the Kuybyshev Aviation Institute, finally earning his engineering degree in 1954.