Error: a function-definition is not allowed here before '{' token|

#include <iostream>
#include <string>
 
using namespace std;
 
bool intro(void);
void room(bool enemy, bool treasure, string description);
string name = "";
string enemyName = "";
string treasureName = "";
const string room1 = "You came through the entrance of the cave.";
const string room2 = "You came forward through the cave.";
const string room3 = "You came to the end of the cave.";
 
int main()
{
    if(intro())
        return 0; // Player doesn`t want to go to the cave. Break programm.
 
    treasureName = "Gold sword";
    enemyName = "Goblin";
    room(true, true, room1);
    enemyName = "Volbata";
    room(true, false, room2);
    enemyName = "Boss";
    treasureName = "Diamonds";
    room(true, true, room3);
    return 0;
 
    bool intro()
    {
        cout << "Hi, player. What is your name? \n";
        cin >> name;
        cout << "We need your help to kill all giblins."
              << "Would You help us, " << name << " ?\n"
              << "Press 1 if yes. \n Press 2 if no\n\n";
        int response;
        cin >> response;
        return !(response == 1);
    }
 
    void room(bool enemy, bool treasure, string description)
    {
        while(true)
        {
            cout << description.c_str() << endl << endl;
            int response = 0;
            do
            {
                cout << "What would you like to do?\n\n";
                if(enemy)
                    cout << "Press 1 to type " << enemyName.c_str() << endl;
                  else if(!enemy)
                    cout << "Press 1 to move to the next room.";
                    if(treasure)
                        cout << "Press 2 to keep " << treasureName.c_str() << endl;
                cin >> response;
            }
          while(response < 1 || response > 2);
            switch(response)
            {
                case 1:
                    if(enemy)
                    {
                        enemy = !enemy;
                        cout << "You killed " << enemyName.c_str() << endl;
                    }
                        else if(!enemy)
                            return;
                case 2:
                    treasure = !treasure;
                    cout << "You kept " << treasure.c_str() << endl;
                    break;
            }
        }
    }
}