Complex sentence: After the Second World War, the company reopened its doors, completely changing its activity in 1948 it began to build motorcycles, scooters and motocarries (three wheeled transport scooters/motorcycles).
Split into simpler sentences: After the Second World War, the company reopened its doors, completely changing its activity. In 1948 it began to build motorcycles, scooters and motocarries (three wheeled transport scooters/motorcycles).