How would I do this?

So I haven't done anything interesting with my hair lately and was thinking of going for a black to dark green ombre look. I already have very dark brown hair which is about the same length as on the girl in the picture. I'd probably get it cut shorter though if I were to dye it.

I'm not confident doing it myself so I'll deffs go to a stylist but I was just wondering if anyone has tried this look before and/or knows how they would do it I.e how much they'd have to bleach my hair, how many sessions it might take etc thanks in advance!

Goal:

My natural colour:

(My hair was still a bit wet when I took this photo it's not grease lmao)