Proof read a number of complex German documents (5000 words)

We develop assessment tests for sales people and our documentation needs to be very precise in its use of language, particularly in the use of specific terms. We have developed a series of assessment tests in German which we now need proof reading and editing where required at a very detailed level. This in itself is quite a complex task and needs to be carried out very carefully and precisely. The work will need to be carried out in an interactive manner involving regular discussions with key members of our team. I am looking for someone who has German as a first language and indeed is completely current with the language, but also has a very strong grasp of English. There are 5000 words in this current work, but if this works out to our complete satisfaction, the there could be a much bigger project behind this.