Documents are viewed by all the users that shouldn't be allowed to view

I'm trying to create a expense tracker using react native. Here i have two user in the ss one 'bangladesh' another 'fayek' . I want documents that are related to bangladesh should only be viewed by bangladesh and refrain fayek from viewing it. Here the issue is both bangladesh and fayek can view each other's data which is not normal in an expense tracker application. How to fix it?

If you turn Document Level Permissions on, only the user that creates a document can read / update / delete it (by default - you can customise those permissions). Give Users on the Collection just the Create Permission