some questions about these phrases (한곡국어)

날 떠나지마
- this phrase means "Dont leave me"

- '날' means '나를' and It's a short word from '나를'. so we can just say '날'.

   나를 = 날.

- '떠' means "go"

  You should know that Hangul is not allowed to use only one word like '떠'

  I think The Chinese can explain something through one word like  '木'[mu].

  but Hangul is that we have to write like '나' + '무' = '나무'.

  So, '떠' This word doesn't work in the sentence.

  '떠나지마' = Don't leave. It's from '떠나다'=leave.

  but In this sentence, It's a negative.

  so, 떠나다(=leave) <-------> 떠나지마(=Don't leave)

Sorry~~I was trying to explain what you want but I know it's not clear~

and it's not  professional answer. but Remember that I wanted to help you. :D

Have a nice day..~ I need to get the certificate to teach Korean.