Bad service.

Hello Peter it's me again On the 3rd of August 2020 i took my car to Vw Newcastle Registration No HH 00 MD GP for radiator repair the diagnostics my car and found that radiator and air con needs to be REPAIRED then I gave them go ahead to fix them, then it was fixed they came back to me tell me that car is still over heating they check cylinder head after they checked it they said the egen is demaged they have to remove it and put the new one, but when I bring my car to repair the egen was fine it was not showing the engine light they removed my egen and put the second hand engen that was bought R32000 Cash after putting the egen thy said I must buy a water pump, was bought and installed after that they came back again and say the car is still overheating the told me the problem is turbo I must buy it R33000 on the second engine that was installed ....MY QUESTION IS HOW COULD A CAR IN VW BE DIAGNOSED AND TOOK OUT PROBLEMS ONE BY ONE. BECAUSE WHEN THEY DIAGNOSE THE CAR IT MUST SHOW ALL PROBLEMES THAT NEEDS TO BE FIXED ALL OF THEM SOMETIME NOT ONE BY ONE WITH DIFFERENT DAYS THATS MY CONCERN AND THE CAR WHEN I BOUGHT IT TO VW REPAIR IT WAS NOT HAVING ENGEN PROBLEM IT WAS JUST LIKING WATER, on the 18th September we went there to see the car we spoke with them and they promised that they will shop around to get Turbo since then we haven't heard from them until we email hello Peter on the 28 September 2020 but even now the car is not fixed they still give us empty promises of fixing our car today is The 12/10/2020 we still don't have the car is stacked at VW New Castle. PLEASE PETER HELP