It’s completely legal to use German proxy services. However, if you doubt whether you can legally use a German proxy service in your country, or whether you can use a proxy service for your intended use case, consult with an attorney who specializes in computer law.
Despite the way that they are often portrayed in films and the media, proxy services don’t make you invisible or invincible. If you are planning to use proxies to do something illegal, or even privacy-focused, proxies might not be able to help you. There are other ways to track you down, and your IP address is just one piece of information.
Two of the providers on our list are open about the fact that they record what their users do. Proxy providers are bound by the laws in the country where they are headquartered. It’s worth investigating what local laws and regulations apply to any provider that you are considering using.