The English lyrics were written for the movie. If you know German, it's not too hard to translate into German.
To you my friend - Nach du mein freund
and you my friend - und du mein freund
and all of us together - und alles uns zusammen
The original German folksong is titled "So leben wir alle tage" and was written in 1706. The lyrics are:
So leben wir, so leben wir,
So leb'n wir alle Tage
Bei der allerschönsten Kneipkompanie.
Des Morgens bei dem klaren Wein,
Des Mittags bei dem Bier,
Vor Morgengrau'n geht's nicht ins Nachtquartier
I had some German friends translate this into English, and they said it was a nightmare to do. The result makes almost no sense because of the differences in syntax and word meaning over 300 years and two languages.
See
http://www.ingeb.org/Lieder/solebenw.html for the music without lyrics.