Germany has a pretty strong call on privacy and individual rights, so It’s unlikely that you will have a problem in Germany (as long as you don’t do something bad e.g. kill someone).
To be hones If I were in your situation I would just use a Faraday bag. It might be a bit of an overkill, but it’s not extremely expensive, and you can have a peace in your mind that your phone won’t make calls.
But if your threat model is low and your happy with the solution you already use, why not stay there?