Unhappy with the car that i had for 8months.

I bought a used 2012 Hndui Elantra gls at Nellas dealership in Prtorua rd, Kempton Park,that was last year August 2021, after signing the documents, I ask for spare key, service history book and maual book, they told me that they dont have,, now I having problems with the car.I called them they say I must take the car to Bosch since the car its still under warrant, now Bosch contacted their Motorite insurance to claim.Bosch diagnosed the car , they required R19 000 to fix the car, Motorite aproved R7 000 they say I must pay R12 000. , this unexpatable since the cat is under warranty.