I think the problem is, that privacy settings need data type “user” instead of “text”.
But I don’t know how to convert an email address (type: text) to an email address (type: user).
And I can’t add users in the Address Book because the input form does not give me the option to select type “user” .
Indeed, you can’t add user from an input form because the only things that you can add inside an input are numbers and texts. These are the two options that I imagine for this use case:
instead of using an input element, choose a searchbox element that allows the user to look for a dataset in your database depending on a text field (ie. the email address).
or you need to “do a search for” a user after each event (ie click on a button) with the constraint “email = input’s value”. In this case you can affect the user to the “Share_with_these_people” attribute instead of the email.