나자기 소개

Using just "나" as a title is a little unusual; I changed it to "self introduction"

저는 미국에서 왔어요.

You don't need to keep repeating the subject in Korean if it's understood what the subject would be.

저는 뭇 잘잘 못 지내요.

왜냐고요?

Using just "왜" on its own like that doesn't fit the formality of the rest of the text. What I wrote translates roughly to, "Why, you ask?"

저 못 알저도 몰라요.

알다 cannot be negated like most other verbs; instead, it has a negative counterpart, 모르다

안녕히 계세요!!

Small spacing error :)