Fetch data from Firebase, update value in Text widget, and auto-update on changes. Flutter

to create data in firestore!
first create a button on place the method in it.

    createData() {
      FirebaseFirestore.instance
          .collection('your collection named')
          .doc("your document id or blank it")
          .set({
        "name": "Jackson",
        "age": 15,
      });
    }

for fetching data you have to create a widget that returns Text;

    StreamBuilder(
            stream: FirebaseFirestore.instance
                .collection('your collection named')
                .doc("your document id or blank it")
                .snapshots(),
            builder: (context, snapshot) {
              if (snapshot.hasData) {
                DocumentSnapshot userData = snapshot.data!;
                return Text(userData["name"]);
              } else if (snapshot.hasError) {
                print(Error); //just for checking
              }
              return const CircularProgressIndicator(); // loading progress indicate
            });

for update a data .
first create a button on place the method in it.

     updateData() {
          FirebaseFirestore.instance
              .collection('your collection named')
              .doc("your document id or blank it")
              .update({
            "name": "Peterson",
            "age": 20,
          });
        }

so you have to use TextField , TextEditingController, to customise your ui perfectly.