There is good German music (Wir sind Helden is probably a good suggestion, likewise Peter Fox - Rammstein don’t like to use complete sentences 
), but for me in the reverse situation books and movies were the way to go, other than interacting with others. Music can be difficult to understand even if you speak the language quite well, in my opinion.
Whether books or movies are better depends on your goals, written or oral communication. It’s a good idea to start with ones that you already know in English and like, so it’s not a boring subject.
Dating a German girl is only permitted if you export at least one girl of equal or greater hotness to Germany.
My daughter studied German, and is getting a degree in it later this month. She watched German translations of American movies, and listened to German music. But she spent a year in Germany at a university, and that is what really did it. She’s going back next year to help teach English on a Fulbright, and will no doubt be really good after that.
She said the first time she thought she really understood the language was when she was listening to a German song while doing something else and realized that she understood the words without thinking about it.
Listen to a lot of Rammstein. Or Oomph! Or Eisbrecher. Or Die Krupps. Hell, any German industrial metal will suffice.
That’s what I do. 
Another good movie to watch in German is Der Untergang (Downfall). It’s the WWII epic of Hitler’s last days in his bunker. It’s the one that has been parodied so much on YouTube. Good plot, good acting, and features the lovely Alexandra Maria Lara. 
I made more progress in 10 days in Dresden than in years of classes in Canada. At the time (1995), the eastern part of a unified Germany didn’t have very many English speakers. It isn’t cheap to stay there for long, though there are cheaper ways of doing it, but in terms of your progress, it’s invaluable.
Beat me to it! Although I was going to say something like “Hold a Bratwurst over his head until he promises not to invade Poland.”
But I *do *get to point out that unless those are magical singing pants he’s wearing, it’s spelled “Lederhosen.” So there!! 
I was going to say the same thing. When I worked with the Germans and was learning, my boss told me to speed up the process and start dating a German women. With their sense of humor…or lack of it, I wasn’t sure if he was serious or not.