What's a substance i can use to bleach my hair? Hydrogen peroxide?

Hair bleach. Hydrogen peroxide at household strength might slightly lighten some hair, or might not, as it's a much lower concentration than whats in the developer that's mixed into hair bleach - which isn't actual "bleach" (sodium hypochlorite) but potassium persulphate and/or sodium metasilicate.

Try it but better to buy some branded dye