How do i go back to blonde after i dyed my hair brown?

it's not a very good idea, it will damage your hair. but do not bleach the whole head. just do highlights all over. keep doing the highlights every few months after it grows out and add some more. eventually, your whole head of hair will look blonde again. i would suggest going to a hairdresser. it will be pricey, but worth it. you may make a mistake at home even if you are being cautious.