[germanier]

Changing your name in general is not easy in Germany. There is a short list of allowed reasons for doing so, each with its own process. Reasons would be things like: Marriage, gender change (in Germany at least one for your first names needs to indicate your gender), unfortunate or funny name, or at naturalization to make your name more German-sounding.

Outside of that it's almost impossible to change your name.

[eru]

However, getting a stage name or artist pseudonym recognized is relatively easy. (But probably wouldn't help a transgender person feel better.)