What should i do to eliminate bad breath forever?

That's a tough one: Forever is a long time, and since our bodies are dynamic and not static, things can change in the future. Bad breath can be caused by cavities, periodontal disease, acid reflux, and diet. Other than diet, the other conditions cannot be 100% guaranteed prevented. It is for that reason that you may not be able to absolutely guarantee your goal.

Probably impossible: Great goal but probably impossible and unrealistic. It assumes absolutely no medical problems, perfect oral hygiene and dental health, and not eating any foods with substantial taste and seasonings.