Dual Citizenship Germany USA

Under what circumstances can a German citizen become a citizen of another country and retain German citizenship?
(Retention permit)

Special constellations arise with only European citizenships, especially since BREXIT for UK citizens.

This applies in particular and under special conditions for the acquisition of US citizenship by Germans with the desire to retain German citizenship. Due to a regulation of the requirements for retaining German citizenship in 2000, it is easier for Germans living in the US who wish to acquire US citizenship to retain German citizenship. The constellation is special if the German-born U.S. citizen (he or she was once German) in Germany wishes to be re-
naturalized while retaining the U.S. passport.

It is possible for an US-American who lives in Germany to get German citizenship and to keep the US Passport.

Can I have two passports?

Yes, under certain circumstances this is possible.