I'm not discouraging, but once you're considering a particular position, please try and talk to previous PhD students of your prospective supervisor. Germany has hardly any fully-funded PhD positions. Instead you typically get employed as staff and have to combine that with your PhD work. The problem is, often professors take on lots of PhD students to get more funding and end up having hardly any time. I've heard stories of a professor having 8 or so PhD students that still wait on him to read their thesis and give the go-ahead for their viva (PhD defense). I'm not saying this is the case everywhere, but it's something to be aware of. So try and find out beforehand.
Sadly, the situation as you decribed is almost the same with PhD students in the lab where I currently work on my diploma thesis and in some around in the institute. Having seen what I've seen (troubles with disertations and giving the PhD defense go-ahead) that's definitely something I want to avoid.
At that age I couldn't care less but now that I'm thinking of doing a PhD in Germany (from what I've heard a very affordable country with many great life science labs) I'm very glad that I remember at least basics even that I haven't actually spoken German for six years.
I think that learning two major foreign languages should be mandatory. Almost everybody can learn one language quite well after +/- 10 years during childhood and to learn at least basics from the second one should not be that much of a problem too.