How long does manzanilla grisi take to lighten your hair? From Black to light Brown hair Naturally.?

I died my hair soft black in November & my roots are coming out from my natural color (dark brown) but now i want to go light brown. I tried dying it but I only got the color in my roots, my ends are fully black. I recently bought the shampoo & conditioner "Manzanilla Grisi" I want to know how long will it take to lighten my hair or is there any faster way to lighten it naturally?