im very new to firebase 9. i just started out as a developer. Could you please help me to understand the following: User SignUp: I am trying to create a user with email, password, displayName.

const res = await createUserWithEmailAndPassword(auth, email, password);

if (!res) {
  throw new Error("Could not complete signup");
}

//Upload user thumbnail
const uploadPath = `thumbnails/${res.user.uid}/${thumbnail.name}`;
const img = await addDoc(uploadPath).put(thumbnail);
const imgUrl = await img.ref.getDownloadURL();

// add display name to user
await res.user.updateProfile({ displayName, photoURL: imgUrl });

//create user document
await addDoc(
  collection(db, "users").doc(res.user.uid).set({
    online: true,
    displayName,
    photoURL: imgUrl,
  })
);

// dispatch login action
dispatch({ type: "LOGIN", payload: res.user });