Complex sentence: He took and active part in organization of Institute of Physics and Mathematicsof Belarus Science Academy, and became the leader of one of four major laroratories there--laboratory of theoretical physics (till 1987).
Split into simpler sentences: He took and active part in organization of Institute of Physics and Mathematicsof Belarus Science Academy. And became the leader of one of four major laroratories there--laboratory of theoretical physics (till 1987).