Hi @UtauyoNASE
If you don't want to move documents to the parent site, you need to give an access to specific users.
Firstly, open documents in Sharepoint (Teams - Private Channel) and then select Manage access.
Secondly, Give permission to users.
Then you can add links to the documents to the parent site.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.