Newt steps or will they come back to me?

I have trade my vehicle at We buy cars Kimberley POD i Feb 2019 and thanks to Lerise Esterhuizen her excellent service . The traiding vehicle was in Midstream. So i got a family memeber to go and test drive the Mercedes Benz ML320 for me. I spoke to David how was the sales person he told me that the vehicle is fully serviced and have the sirvece book. And that there was no problems on the vehicle. He told me that there is only one problem and that was that the aircon light is on but i can let them just reset it at Kimbetley. The car was test driven but David only gave about a 1 km distance to drive the vehicle and was not allowed to go over 60kmph. I got there in Jhb at Midstream to collect my vehicle and the same thing i was not allowed over 60kmph and also just 1 km drive. He also told me that law indicate that i get a 6 months warrenty on the vehicle There was no light comming on at that stadge. On my way back to Kimberley that same day the car started to struggle after 100kmph and then the light came on witch was the break alarm for break wear. I tried to get the car through roadworthy witch David also told me that it was done i can just put it on my name. Well i could not get the car through the roadworthy because of the breaks fulty lights and gearbox . The car is still on we buy cars name and it cant drive. I spoke to one of the manegers and he told me there is nothing they can do for me. Wow thats service. I have the vehicle now for almost 2 months and its gearbox is still broken. I send a eamil to Gerrie also but i did not even get a respond. I am not going to leave this matter here. I need my vehicle to be fixed on there expences or a refund.