I grew up bilingually, speaking both English and German. In addition, I have three years of experience translating news summaries for an international media agency (Kantar Media) and lived in Germany for eight years before recently moving back to the USA.
In addition, I've done around 20 hours of German-English transcripts on a medical topic as part of an earlier project on this site. In my experience, one hour of German audio equals about 3 hours of work (with good audio quality, barring heavy accents etc.), resulting in a bid for $45 per one-hour project, with freelancer.com's project fee on top.
I am bidding on one of the hour-long audio files, but could do up to one per day this week. Any additional work could be added on via milestone. Hope to work with you!