What happens when i get a hair relaxer?

Well i have relly puffy hard hair. well im mexican and well like i cut off half my hair and wore a wig and like its been a year now and my hair hasnt grown much and im gonna get my hair relaxed with organic root stimulator olive oil built in protection no lye relaxer. so people tell me that it only last for four weeks? so What would happen to my hair after 4 weeks? will it go bakc to being hard and puffy ? or will it be a little straight but puffy and wavy> my hair is kinda wavy too :'( i dont knoe what else to do with my hair.