Car dealer refused to reverse the car deal/transaction with in 14 days

We have bought bmw x3 second hand (3.5 years old) from willem cornelissed automative b.v. we received the car on 8th july.first, we had an issue with ac of this car while driving back home then we went back to their centre to get it fixed. i drove the car to the office on 11th july and car stopped in front of my office parking garage without giving any warning caused a lot of traffic and blocked the way. there is a bmw authorised dealer infront of my office. we called the mechanic, he couldnt do anything then i called bmw service assistance and bmw assistance person couldnt do anything either. as a result, car had to be towed and returned to the dealer. after that stressful incident, we tried to contact the dealer and trying to reverse the deal however dealer keeps saying he is quite busy and attending the other customer. we have informed him in writing in an email within 14 days of purchase that we would like to have our money back and return this car. i am not confident with this purchase and would like to have our money back. the dealer refused to return our money back and behaving in a very unprofessional way. please let us know how can we solve this.