Welcome to the board.
There are several ways to do this. One way is to define Custom Views, in which rows/columns are hidden, for each View. Once these are named, you can attach them to buttons to have a macro show just that view.
For a more detailed approach, you could have them sign in with username, check that against a username file, then add an extra step for password. Once that is "passed" you can provide only their specific Custom View. When they are finished, you could have an End button that with code, would hide this sheet, and take the person back to the login page. Of course, you unprotect and reprotect within each code, which the user never sees.
I have done this for a different project, if you are interested.