Complaint on Hyundai poor services

I bought a second hand car, most of the things were to be done after the signing of the paperwork and I was verbally assured that it will be a quick fix. They did some of the things (service and fitment of some parts) which took 3 weeks as it had to go for some rework fixing (paint job). The salesman did not even bother responding to my whatsapp messages as I wanted feedback on what is happening even worse I had to go as far as writing emails for the car to be fixed faster (the manager had to intervene). I did not even enjoy my car for the first month as when it came the installment was due already, paid tracker the first month for a car i did not have with me. At this point the car is out, the salesman is blue ticking me with the outstanding things when I send whatsapp messages. I do not have a copy of the Natis paperwork, outstanding parts not fitted and some problems not attended to. I do not even have the spare key as they said they will sort it out for me. I am always after them and it is not fair.