Bmw supertech Newcastle negligence

In May 2017 I bought the car( BMW 420i, M sport 2014 Model from BMW supertech Newcastle. On the collection day I was told that the car had no spare key but I must come back the following week to collect it because apparently the spare key was at BMW supertech durban because the first owner of the vehicle traded in the car in durban. When I came the following week, I was told that they couldn't get hold of the previous owner to bring in the spare key so they 're gonna order me a new spare key. The following week bmw supertech newcastle phoned me and told me to come to the dealership to collect the new spare key and I went there and collected the spare key. In June 2018, my spare key got lost and the police advised me to deactivate the lost spare key. I went to bmw supertech newcastle on 14 June 2018 and I paid R917. 00 and they deactivated the key and they gave me the invoice which I still have. On 25 September 2018 my car was ****** at about 20h00 at night and recovered by the police at 00h00 midnight on the same day. When they found the, there was a key inside the car and when tested, the key was working on the car. Then I reported that matter to bmw supertech newcastle, and they said that is impossible because they deactivated the spare key which I lost in June 2018, but they said I must bring in the car and the key that was found inside the car so that they could do technical investigation and the matter was also reported to bmw south africa. During the investigation it was found that the key they deactivated was actually the spare that was not received from the first owner of the car last year when I bought the car. The salesman who sold me the car told them the whole story about the spare key when I bought the car. Now the problem is, the car was damaged on the front bumper, control arm the front left wheel broke and the left side of the vehicle got scretched. The manager at BMW supertech Newcastle said they can't help me in any way because the key that they ordered for me doesn't reflect on the system whereas the car salesman confirms that the car spare key was actually ordered by him last, but the manager insists that they won't take responsibility and I must involve my legal team if I want to, because they won't investigate how I got the new spare key because that is not their job. It's been over a month now without a car and I'm financed by bmw finance. What must I do?