EXTREMY BAD BAD SERVICE RECEIVED

Good day , I Purchased A 2008 BMW 523i series on the from Car to cash on Tuesday 27 April 2021 ,was being assisted by their consultant Name Almighty I was advised that the car only needs a battery to be replaced ,on the same day I bought the new battery to my surprise the next day the car doesn't start anymore . Immediately called the guy and informed him of the situation he did not provide any help except that i should call a mechanic ,i called in the mechanic to inspect the vehicle at my own cost i advised was told that the cam belt ,brake pad ,control arm bushes and coolants and other parts on the engine where not aligned well and not functioning properly. I wouldn't have purchased the vehicle had they have been honest with me from the onset ,,,,It really breaks my hurt to be unfairly treated like this ,Almighty promised that he would speak to management i called him many many times the whole of last week with no feedback ,i only asked to give the another car within the value which they do have... After my call with him this morning he again told me that they are willing to take the care back with R30 000 ,I mean i purchased the car with total value of R44 000. How is this a good business practice Please help me because i need to have the car now.