Bad service

In October 2018 I brought a ford Fiesta ecoboost 1.0 (2016) pre used at Steven's motors Kempton Park. The cars was in good condition, after three months of driving the car it started to overheat and stopped working. The car was towed to Casseys Auto Springs Ford, and at Casseys Auto Springs Ford they told me that the car was drove for long distance without water and oil and that effected the engine of the car,Of which it was not true because everytime when I went to the garage I asked them to check for water and oil.they just wanted money because they quoted me about R40k to replaced the engine and told me it not covered by warranty . Because I didn't have that amount of money I took the car back and I tried to complain where I brought the car they didn't help me they just said I damaged the car and all sorts of stories.. I was confused and didn't know what to do I had to see for myself how I fix the car because I needed it. it's has coursed me so much financially and emotionally, only to found out when I do my research that the Ford ecoboost 1.0 engines have overheating problems .I want hellopeter to please assist me with my problem, because Casseys Auto Springs Ford has disleaded me because they only wanted money without investigating what is the really course of the problem.i need your help in terms of the lost incurred due this, and making sure the car is checked that it is 100% safe for me to use.