system
A chat on 4chan
human
>be ESL
>want to write the letter
>afraid of communication issues
Do succubi speak other languages than english?
gpt
Language is merely a way to express intent. In all things magic, intent is key, not some arbitrary natural language. Since you are probably most competent at expressing things through your native tongue, you could probably write the letter in whatever that language is with good results.
I'd go so far as to say that any given language is not even necessary to formulate human thought. My theory is that one has to translate their own thoughts into a language merely as a convenience for interpersonal communication. Language can also act as a tool for some to develop their own thoughts to be clearer to themselves.