Student Exchange Programs

One of my good friends is German. He’s an exchange student, and is perfectly enabled to drink at his age - in Germany. But he drinks so much, and last time he did something horrible and couldn’t even remember. He says it’s because everyone drinks in Germany. He doesn’t learn from his mistakes, obviously, and wont listen to me when I tell him I don’t even want to talk to him when he’s drunk because he acts so stupidly. How do I get him to stop without making him think I’m too much into his business?