Problem with data linking in firebase with my listview

Hi everyone! I have an urgent need to solve this problem due to connecting data present in a database created with firebase and my listview.
I need my project created with app inventor to print the data present in the database connected to my website in my listview, more precisely I would like to print only the emails in the listview.
Everything works correctly, however it seems that when capturing the email Firebase does not detect the email label and puts the null value there. Can you help me? I would be extremely grateful ... Below I attach screens of the code and screens of the database, and possibly of the interface


there is no tag named email DIRECTLY under bucket Utenti.

ah ok thanks, but every time users register on my site in my db I will never know what the bucket above the "email" tag will be, because it is generated... what can I do?

How do you save the user register information? by AI2 blocks?

from my website in javascript, i send u the script?

You are using post function in js, which is not implemented in AI2.
In this case,You need to use Web componnet to get your user info. Search the forum for an solution, esp from @TIMAI2 , he is expert on this.
or read this:
Firebase with Web Component - Tutorials and Guides - MIT App Inventor Community

The UID for the user will/should be returned to your website, can you capture it from there ?

or as @Kevinkun suggested, sign up your users from the app directly, using the web component.