Long-
just purchase a one way ticket to Berlin... that easy... if you're on a budget go 2nd class, just like in the good ole USA. If you're on a *real budget* try hitchhiking
Oh yeah.. the proper french sentence to purchase your ticket would be
"Un billet pour Berlin, s'il vous plait, premiere classe, allee seulement"... You got some time to try to memorize this, so practice, dude!
Otherwise try good ol' plain english... Many europeans do speak the language, y'know - especially at train stations & airports!
Avec mes meilleurs voeux de bon voyage, und gute Fahrt!!
Paul