write data in firebase Realtime database web

i am beginner with firebase as web, so i am tring to write in the database i was trying to make nested loop but i figure out that i cant even write in my database at all..

i looked in firebase documentation (https://firebase.google.com/docs/database/web/read-and-write)

function writeUserData(userId, name,phone, email,password) {

    database.ref('users' + userId).set({
      username: name,
      email: email,
      password: password,
      phone: phone
    });
    userId+=1;
}

but after that i tried to just write simple thing like

const database = firebase.database();
const ref = database.ref();

ref.set('Hello, World!');

i tried to debug on the browser (if there any other way to debug you can let me know) and see if there are any problems found but all i found is warnings enter image description here

and it didnt write in the database. does this do anything with rules or something (please can u justify what does rules do ?) ? just in case here is the pic enter image description here

other pic that i found other people have problem with that they discussed on stack overflow enter image description here