First of all, thank god you and your gf survived from that accident, secondly, about the car, I personally had a accident before, driving 120km/h hit divider but my car didn't turtle. My car had a lot of problems even after repairing, I totally think it's the mechanic's fault, they are so unprofessional and ah beng ah beng style one. Now they have made my car even worse than ever before.

So in my humble opinion, if you don't want to spend money on buying a new car, at least try to get a good and experienced mechanic. Pricier a bit never mind lar as long as they know what they are doing.