I'm an new DM (only 7 sessions under my belt) and one of my friends has been troubling at best.
He has been looking up rules and disrupting the game even after I have told him the rule 20 times. He has also been looking behind my DM-screen to get the rule-book for rules I have already explained to him.
He's also talking back to things that happen, like he got [redacted] cut off and he replied that he had no [redacted] which was just absurd (keep in mind he said this as it happened not while he was creating his character).
What do I do?