WANT TO RELAX MY HAIR.ANYONE WHO HAS PLEASE LET ME KNOW IF IT WENT Ok?

well i have hair like corinne bailey rae but longer to my shoulders,and i hate it,i want it relaxed.just want to know if you think it will break my hair if i use a kids or i was thinking of using this new softsheen for fine hair relaxer.will it be ok? what do other mixed race girls use?