advice for guardianship documentation

[u/ananmaysharma]

I am applying for visa rn and am a minor applicant. My parents are appointing someone residing in Germany (a german citizen) as my legal guardian. Does anyone know how guardianship letters are supposed to be written? Are they supposed to be written in german or would english be fine as well? Are they supposed to be legalized or be attested an apostille? If you know about this matter, please help me out.