Car dealership ( Next drive Auto)

Please note that on 17/12/2025 I bought a car at NEXT DRIVE AUTO in Montana, I only drive less than 3 months the the car stuck and when I take the car back the Owner his name is Shaun Nel doesn't want to fix my car he says is my fault and according the law the warranty must be 6 months. I don't recommend anymore to go and buy the car there they don't have good service and they don't sell the good condition car. Can anyone advise me what must I do with this situation.