Yes, it's mostly fine doing that. The German law is incredibly stupid in the context of international law anyway. The issue is that citizenship is stricly a co

Yes, it's mostly fine doing that. The German law is incredibly stupid in the context of international law anyway. The issue is that citizenship is stricly a country own prerogative outside of the agreement not to make people stateless. So Germany is free to tell you they won't give you the German nationality if you don't renounce your other ones and is free to strip you of your German nationality if they find you have another one. Meanwhile, the other country can still consider you a citizen if it wants to. That's its sovereign right and it doesn't have to agree to you asking not to be considered one.