I don't think you will learn much from doing a copy of a Picasso piece (unless you copy some of his older work which was realistic).
I would suggest copying some earlier Masters, like Rembrandt, Vermeer, Pieter Bruegel the Elder, Albrecht Dürer, Da Vinci, Michelangelo.
That kinda stuff. That and real life studies, draw what you see.
Making a copy of stuff like Picasso can be good at a later stage, but only if you not just copy it, but THINK about why he did stuff how he did it. Like composition, colours and whatnot.