How could a guy stop masturbating ?

You can't: Between puberty and at least later middle age, it is impossible for most normal men to go for more than a few days without an ejaculation by whatever means. If you're married or otherwise in a relationship, fine. Otherwise, if you try heroic abstinence, you'll end up having trouble working and even going to sleep. Don't make life even harder -- there's no reason not to enjoy yourself.

Marriage, maybe: All single men do this and most continue at least occasionally into married life. It's basically a good thing -- it keeps you focused, it's fun and safe, you learn about your mind and body in preparation for being a grown-up, and only ideologues have problems with it. I'm going to assume you do not have an obsession with erotica that interferes with other important things. Talked with dad? Cheers.