What's wrong with my car?

it's a brand new honda civic...it backfires and it's so embaring! i was leaving my friends house and he told me to never buy a honda...and as i was pulling away it sounded like a gunshot...also, when it gets into overdrive and then i slow down, the car is like working against the brakes...i have to push really hard on the brakes to make it stop and then it dies...then it starts again fine...whats going on????