Create a sharing-only user account on Mac
If you want to give someone limited access to your computer, you can create a sharing-only user account to enable the person to access only the files and folders you specify.
On your Mac, choose Apple menu > System Preferences, then click Users & Groups.
If the lock at the bottom left is locked , click it to unlock the preference pane.
Click the Add button at the bottom of the list on the left.
Click the New Account pop-up menu, then choose Sharing Only.
Enter a name and password for the user.
Click Create User.
You can also create a sharing-only account for one of your contacts when you set up file sharing.
You can also specify which users can share your screen.