I don't know about Germany and how to proceed, but someone should have responded to you so perhaps the email address was wrong or an old one.
However, you should not lose your British citizenship; it is only certain countries that would make you renounce your citizenship of birth and I don't think that Germany is one of them.
What would you put in Room 101?
Does anyone have a really simple diet plan?
Change the name in a tv show /movie title to the above user username


