Quality of C-class 2012

I bought a C200 in 2012. I bought a demo from mercedes Benz. I several times in taking the car in for some service had reports issues that as a Woment I picked up on the car and none were seen to be a problem. The car had terrible smoke from the back and a noise as if im starting a desiel car. In March the car stopped at somerset east three hours later a technichian aarived on site and found nothing wrong with the car. I then drove back to Cape Town. Three months later the car stopped on my way from George in Caledon. It was then towed and was informed that the petrol pump is a problem. It was replaced. Wednesday last week i look the car in for Service still complaining of the same sound and smoke from the back of the car. Now I am informed it is a gear box and timing chain. I would like to know now excatly what is the quality of the mercedes benz we buy these days . at 82000km the car has been several times in for repairs of a consistant fault. Are these not factory faults which are transfered to the customer for customer account to fix. I need to understand as this is not the first car bought in 2012 c200 with the same problem. a is also experiencing the same. Enquiery please