Frustrated

Very unhappy bought car from nissan umhlanga in June 2017 (Brand new car) car has faults it goes to dealer when I get it back after few days or weeks problem is back. I fight with manager from dealer so often but I am not being taken seriously I am just so frustrated I don't know what to do anymore I am feed up and frustrated Nissan Umhlanga is not taking me seriously as when I owned a send hand car never had issues the way I am having with a brand new car