Saving document from Firestore database in Flutter

I am trying to get a document from the database where the users can put in an email and it will pull the document and save it so I can use the document in an editing module. Here is my readUsers method

Future ReadUserinDatabase(String email) async {
  Stream<List<DatabaseUser>> User = FirebaseFirestore.instance
      .collection('Users')
      .where('Email' == email)
      .snapshots()
      .map((snapshot) => snapshot.docs
          .map((doc) => DatabaseUser.fromJson(doc.data()))
          .toList());

  print(User.map);
}

I will be grabbing the document ID from the returned document so I can put it in for doc to edit

Future EditUserinDatabase(
    String oldemail, String newemail, String oldrole, String newrole) async {
  final docUser = FirebaseFirestore.instance.collection('TEST').doc('Doc ID goes Here');

  await docUser.update({'Email': newemail, 'Role': newrole});
}

The error that is occurring is when I print User.map it is not printing the information in the document it is printing '$user' and is not saving in a form I can use it. How do I save the document