The Edit user action is only possible for an individual user.
In the following is described how you can edit the user data:
In the user table, in the desired row, click on the Edit action.
-> The Edit user page opens.
Change email address
In the Access data section you can change the email address with click on Change email address.
In the Contact details section you can edit single contact information.
In the Preferences section you can change the language in the list field.
Finally click on Save.