ostream and ofstream operator overloading ambiguity problem

I'm trying to overload ofstream and ostream operators but I have a problem. I'm saving active game while using ofstream and printing on terminal by using ostream.

Here's the error I get:

hex_game.cpp: In member function ‘void Hex::saveGame(const string&)’:
hex_game.cpp:375:18: warning: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second:
  375 |  myfile << (*this);
      |                  ^
hex_game.cpp:193:11: note: candidate 1: ‘std::ofstream& operator<<(std::ofstream&, const Hex&)’
  193 | ofstream& operator <<(ofstream& fileOutput, const Hex& obj){
      |           ^~~~~~~~
hex_game.cpp:207:10: note: candidate 2: ‘std::ostream& operator<<(std::ostream&, Hex&)’
  207 | ostream& operator <<(ostream& outputStream, Hex& obj){

LINE 375:

 void Hex::saveGame(const string& file_path){

 ofstream myfile;
 myfile.open(file_path);

    myfile << (*this);
    cout << "Game has been saved!" << endl;
    myfile.close();
}

Definition of ostream [FOR PRINTING THE BOARD ON TERMINAL]

ostream& operator <<(ostream& outputStream, const Hex& obj){
    if(obj.getGameplayType() == 1){
        outputStream << "Player1's Score: " << obj.getScoreP1() << " points" << "  |  Player2's Score: " << obj.getScoreP2() << " points";
    }
    else{
        outputStream << "Player's Score: " << obj.getScoreP1() << " points";
    }

    outputStream << "\n\n ";
    for(int i=0; i<obj.getBoardSize(); i++){
        outputStream << " " <<obj.hexCells[0][i].column;
    }
    outputStream << endl;
    for(int i=0; i<obj.getBoardSize(); i++){
        outputStream << i + 1;
        if(i+1 < 10) outputStream << " "; 
        if(i >= 1){
            for(int j=0; j<i; j++) outputStream << " ";
        }
        for(int k=0; k<obj.getBoardSize(); k++){
            outputStream << " " << obj.hexCells[i][k].point;
        }
        outputStream << endl;
    }
return outputStream;
}

Definition of ofstream [FOR SAVING THE ACTIVE GAME INTO A .TXT FILE]

ofstream& operator <<(ofstream& fileOutput, const Hex& obj){
    fileOutput << obj.getGameplayType() << endl;
    fileOutput << obj.getBoardSize() << endl;
    fileOutput << obj.getTurn() << endl;

    for(int i=0; i<obj.getBoardSize(); i++){
        for(int k=0; k<obj.getBoardSize(); k++){
            fileOutput << obj.hexCells[i][k].point;  
        }
        fileOutput << endl;
    }
return fileOutput;
}

I searched my answer on net and I get some help but I did not fix this error yet. I fixed other ambiguity problem by adding explicit keyword before Hex constructors but this one is not fixed. Can someone help me?

(I must overload << for both ostream and ofstream. This is my homework and my teacher wants like that)