Super faulty engine

I bought OPEL CORSA Z14XEP complete engine from them at a price of R12k. The engine was installed by a qualified mechanic and was approved for warranty of 90 days. After only I drove the car 500km the engine started smoking. They recalled the car into their workshop. A new engine replacement was done and was happy. After I drove the newly replaced engine another problem came, the car was not revving up and the head gasket was blown. I called them and ask me to bring the car back to their workshop. Afternoon over than 3 weeks the car is been released with the same problems not fixed. I have lost time and money but nothing has been done. Their workshopmanship is not recommendable. Please be careful with this company