Audi A3 horrible

I was happy to be a proud owner of the new Audi A3 1.6 TDI sortspack until I started experiencing serious mechanical problems with it. First they told me it's the wrong diesel I put in the car but even after taking their advice to only use Sasol or engine products, the engine lights faults contimued to appear on my car. About 5 times I took my car back to them to fix but the problem still persisted. My last visit there was barely two weeks ago and barely two days of driving the car after repairs, it gave me problems again. I asked myself questions