Hjelp til klage på bruktbil

I am writing to seek your assistance regarding a dispute arising from the purchase of a used vehicle in Norway. I purchased a used Honda Civic 1.4 (2007) from a company. Shortly after the purchase, the vehicle developed a fault, despite assurances that it was in good condition. I have repeatedly attempted to contact the seller to request that the fault be addressed and the vehicle repaired in accordance with our signed purchase agreement. However, I have received no satisfactoctory reply.