Ive had a broken nose since childhood, i could never breath properly, if i get rhinoplasty is it a given that my breathing will be normal then?

It depends: It depends on what is causing the difficulty breathing. You should consult with an ENT to see whether you would benefit from this procedure.

Rhinoplasty: Nothing is guaranteed, but certainly seems like it will help somewhat.

Depends: see a facial plastic surgeon experienced in septorhinoplasty which treats both the inside and outside of your nose. If you have a deviated septum and that is treated simultaneously you may well breathe better after surgery. There are other nasal disorders that the surgeon can check for during your consultation.