Well, now that you got it worked out how to save the data to two different collections, I’ve gotta ask why? It would be much better to have only one collection with everything saved, and have a field for gender. This will result in streamlined code, and will be much easier to maintain.
You can achieve privacy by ensuring that your collections have proper permission settings, and by performing all of your database queries in backend files. As the site owner/admin, you can access all of the collections in backend code, while regular site visitors/members will be blocked.
You don’t need to “divide members by category”. You can achieve the proper level of privacy and security by performing a query of the collection based on the ID of the logged in user. That person’s data will then only be available to that person and no one else.