3D Mask file correction and splitting

I have a mask stl file i want to edit, the only edit is to edit it so the eyes hole can be perfect with the eyes of the head scan I'll send, also to add a back cover for the mask, ill send you a picture of how the back should look, and lastly, to split some spercific parts where magnets will be added, I would have done it myself but my aunt died and I'm very busy with a whole lot, so please once you message and I reply you, please be active because I don't really have time. I need it ASAP.

Once you submit your proposal, I'll send you the file immediately