Either or, it won't cause any difference in sexual function unless it's uncomfortable because of the pressure in your bladder. It's hard to piss while erect though. So I suppose you may as well do it before...
You'll normally have the need to pee shortly after masturbating anyway - Nature's way of clearing the pipes.
...Whether 'tis nobler in the mind to suffer the slings and arrows of outrageous fortune or take arms against a sea of troubles. OK, your'e right...before it is!
It doesn't matter if you take a giant leak before you whack off, you're gonna be peeing after. A raisin in the sahara would pee right after he whacked off. If raisins lived in the sahara. And whacked off. I call it Post Masturbatory Urination. Or PMU.
An interesting condition, only PMP (Pre Masturbatory Pissing) is even crazier! But I do agree a raisin living in the Sahara, or any desert for that matter may prefer to whack off in a PMU situation! Professor Blithering Von Kocksuk has written endless boring books on the subject. A 'must read'.
any other book about this very important item i dont know what to do to pee before or after masturbation
The Benedictine monks were adamant, I quote from a 15th century book:- Pro mastubare sed pistus est puereque sed non fortuna! I think that answers your question.
It's best to use the bathroom before sex or masturbation - best for anal sex for obvious reasons, and best for masturbation because you can enjoy the afterglow without being disturbed by having to urinate. There isn't a need to "clear the pipes" by urinating after sex for men or women, your penis self-cleans on the inside.
I do it after when wanking but for sexual pleasure enhancement, i pee before sex. it keeps everything on track better...