lior please check this policy https://aamplugin.com/policy/allow-a-user-to-manage-only-one-page. If you install it and attach it to any desired user, it will do all the necessary magic for you.
If you want to go traditional way (with AAM UI), then you need to define default access to all pages and check HIDDEN, EDIT, DELETE, PUBLISH options on the Posts & Terms tab for the Pages post type.
Then you can drill-down to Pages, find your desired page and uncheck those checkboxes.
Note! Prior to doing all these steps, make sure that you switched to correct user on the Users/Roles Manager panel.