Complex sentence: It adopted a new constitution based on the Soviet model, abolishing the position of President and Prime Minister, with Castro taking on the presidency of the newly created Council of State and Council of Ministers, making him both head of state and head of government.
Split into simpler sentences: It adopted a new constitution based on the Soviet model, abolished the position of President and Prime Minister. Castro took the presidency of the newly created Council of State and Council of Ministers, making him both head of state and head of government.