I've lived in Zurich for the past 2 years, originally from Toronto, Canada
I've travelled quite a bit of Europe in my time here, so here's a few tips
1. anyone who says Germany/Europe/whatever sucks is an ignorant north American. They don't understand or appreciate other cultures. You'll notice quickly that there are things that are better and worse about another cultures. Embrace those which you like, respect those which you don't. Be open minded, it'll pay off in spades
2. you're going to a good spot for travel. Bonn isn't that exciting from what I hear, but its central and there's lots that you can reach in a short distance. If you're there for 3/4 months the spots most important spots i'd say you should visit would be Amsterdam (even if you don't smoke it's an awesome city), London, paris (despite its rep it is a great city), and the Austrian alps (Innsbruck, don't bother coming to Switzerland, Austria is more authentic and half the price). I don't know if you're old enough to drink, but Oktoberfest in munich is also amazing. In terms of travel, book everything EARLY. Like 4 months in advance early and i'm not kidding. Flights/trains in Europe can be super cheap, but you have to book way in advance. Check easyjet and ryan air. You have to meet certain luggage and the flight isn't comfortable but who cares. Pick the things you want to do now and start booking.
3. make an effort to learn the language. Download duolingo now (its free) and do a lesson a day. It adds up quick and it'll allow you to get through everyday transactions without feeling bad for making someone else have to speak broken English. Even if you start in german and ask people if they speak English in german, they'll generally recognize the effort and be more helpful
that's a quick guide, but most importantly have fun!