firebase authentication not working in android studio app?

Question

Android

I will give a link to the git: https://github.com/HoboHub/gramophone_login
The problem is most likely in the MainActivity:
https://github.com/HoboHub/gramophone_login/tree/m...
What is the point: When you enter the application - only the registered user is thrown into SetupActivity where he enters his data (country, name, nickname). After it should be thrown into MainActivity, marked: registration successful, congratulations!!!
In fact: Only congratulations pop up. The user is transferred to MainActivity for half a second and then enter data back into Setup.
Here is the code from Main.
If there is no user data in the Firebase database, it is thrown into SetUpActivity.

private void CheckUserExistence() {
        final String current_user_id = mAuth.getCurrentUser().getUid();
        UsersRef.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                if (!dataSnapshot.hasChild(current_user_id)) {
                    SendUserToSetupActivity();
                }
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });
    }

I thought to do it through else (if there is data, then ...), but it's not clear to me what to write, because the user initially starts from MainActivity and, in fact, if he is authorized, he must remain there.
SetUpActivity

Second transfer to Main and back

Answer 1

Okay, I figured out what the problem is. I put quotes in the wrong place in SetUpActivity