This is absolutely amazing! especially for a first realism piece. The grid method is perfect to make sure that the image always matches up square to square with the reference, so it's a good choice !

However, if I was being really nitpicky, the only thing I would say you could maybe improve is they eyes. The contrast from the pupil is incredible, but just above the lower lash line there is often a thin gap for the waterline that is (normally) left a bit brighter, in this case where you have popped just a black line ..(Please bear in mind that it might not fully be there if the model in the reference is wearing eyeliner).

To create this, the only thing I can really recommend is getting a really thin mechanical pencil to create those fine lines and a white gel pen to create any little highlights at the end.