Complex sentence: They started building steering boxes for different types of vehicles (construction machinery, etc.), they abandoned the production of medium-sized tractors and focused the production in tiller, motocultivators and small 4-wheel drive tractors.
Split into simpler sentences: They started building steering boxes for different types of vehicles (construction machinery, etc.) and focusing in tiller design and construction. Subsequently, they added to the factory's production, motocultivators and small 4-wheel drive tractors.