BAD SERVICE/EMPTY PROMISES

I bought a BMW X3 in July 2018. I noticed issues within 2 weeks of having the car. I notified the dealership and they promised to fix it. I have spoken the Workshop Manager and Mohamed and to date I am still waiting. I also sent an email to Phillipa and called her but to no avail. I don't know what to do anymore- I have been calling almost every week and only EMPTY PROMISES. What and who will be accountable if something happens to me and the car whilst driving it?