Poor quality of Oplel Astra

I bought an open Astra in December 2012, it was a second hand and had not even reached 28000km. Since I have had this car I have had to take it for repairs more than 10 times. Worst of all, for the past year it has spent more that 5 months at the dealership being repaired, and Iv had to drive a cheap courtesy car, despite the high instalment that I'm paying monthly. Mind you the car has not even reached 70000km. I think the car is very poor quality, I regret the day I bought it and I will NEVER buy a GM car again. I wish I could ask for my money back from the dealer who sold it to me.