Hire a pro!
Value for money - There are a number of translators who offer their services for cheaper prices. You are running the risk, though, to entrust someone with translating your documents who may speak the language very well, but is not a professional translator. For in Germany everyone can call themselves a „translator“; it is not a protected title.
Translating is more, though, than just putting words from one language into another. It is a trade that has to be learnt. A good translator should be able to give proof of their qualification, for example by diplomas and certificates. Also, being a member of a professional organization is a sign that you are dealing with a professional who is able to meet certain quality standards.