As said before, I doubt there is any public data on the use of Bitcoin mixers.

However, there is a big German Bitcoin community and it’s pretty likely that there is a strong demand for a reliable mixing service. There are some other services already, but if you’re here for the long run, I am sure it makes sense to focus on the German market as well.

I don’t know about your marketing budget, but I guess it won’t be a bad idea to add a decent (!) German translation. If you need any help, I am sure there are many capable German users on Bitcointalk who could help with a translation.