Translation:I am a citizen of the Federal Republic of Germany.
Anything particularly wrong with "Federal German Republic" over "Federal Republic of Germany"?
Is it necessary to say Federal Republic of Germany? I just wrote Germany and it was wrong.
In practice, no, it's not necessary, because it's the same place (just as saying "the US" and "the United States of America" are understood to be the same thing). But this exercise is about translation and understanding words, so since "Bundesrepublik" is in the German sentence it would be necessary to translate that to English to ensure the same meaning (that is, to be using the official "long" form in both languages(