Help with file io decision making

[cmparks10]

Hello there! I am working on a C++ program that is like a faux bank account. I have the program set up to be able to get a username, search a file for the username, find the associated "balance" with that name, and change it from there. I found the best way to change a text file is to just write a new file with the changed information inside of that. Here is the code I have so far, but it isn't giving the results I want. Keep in mind this is in a very early stage.

#include <iostream>
#include <fstream>

using namespace std;
//function prototypes
void addUser();
void part1();
int main();

//global variables
    string username;
    string password;
    int balance;
void addUser(){
    //open a file in write mode
        ofstream myfile;
        myfile.open("userinfo.txt", ios::app);//append the text file
        if(myfile.is_open()){
        cout<<"Please Create a Username: ";
        string inputCheck;//a string to compare name
        cin>>inputCheck;
        cout<<"Please Create a Password: ";
        cin>>password;
        cout<<"Current Balance: ";
        cin>>balance;
        myfile<<inputCheck<<' '<<password<<' '<<balance<<"\n";
        myfile.close();
        cout<<"User account '"<<inputCheck<<"' has been created"<<endl;
        }//ends create a password else
        //ends if userCheck is open
    part1();
}


void part1()
{
    cout<<"1.Add User\n2.Edit Information"<<endl;
    int input;
    cin>>input;
    if(input == 1){
        addUser();
    }else if(input == 2){
    //find the user

    cout<<"Enter the username: ";
    string checkUser;
    //string checkUser;
    cin>>checkUser;
    ifstream infile("userinfo.txt"); //CREATING IFSTREAM
    ofstream outfile("pleasework.txt");
    //user.open("userinfo.txt");//open the file to be read in
    //if(infile.is_open()){//find the user
    bool foundUser = false;
    while(infile>>username>>password>>balance){
        if(checkUser==username){
        foundUser = true;
        //cout<<"User: "<<checkUser<<" Pass: "<<password<<" has been logged in"<<endl;
        break;
        }
    }
    if(foundUser){
    cout<<"Current Balance: "<<balance<<endl;
    cout<<"Enter new balance: ";
    int newBalance;
    cin>>newBalance;
    if(infile.is_open()){
        outfile<<username<<' '<<password<<' '<<newBalance<<endl;
        }
    }//end input 2
    else{
        string content;
        getline(infile, content);
        outfile<<content;
    }
        infile.close();
outfile.close();
    }

}//end main

int main(){
    part1();
}

after running:

user1 pass1 43
user2 pass2 550
user3 pass3 65

[cmparks10]

It's going to be something like:
open read and write filestream
for each line in the text file
if it is the line we want
edit the line and put it in the new file
else if it isnt the line we want
put the unedited line in the new file
close the files
fin

[gunnerfunner]

#include <iostream>
#include <fstream>
#include <sstream>
#include <string>

using namespace std;

struct bankAc
{
    string m_username;
    string m_password;
    string m_balance;
};

ofstream& operator << (ofstream& os, const bankAc& bA)
{
    os << bA.m_username << '\t' << bA.m_password << '\t' << bA.m_balance <<'\n';
    return os;
}

int main()
{
    ifstream inFile("F:\\test.txt");
    ofstream outFile ("F:\\test1.txt");

    bankAc bA;
    cout << "Enter name to search: \n";
    string name;
    cin >> name;
    bool match = false;
    if (inFile)
    {
        string line;
        while(getline(inFile, line))
        {
            stringstream stream(line);
            stream >> bA.m_username >> bA.m_password >> bA.m_balance;

            if(bA.m_username == name)
            {
                cout << "Name found, enter new a/c balance: \n";
                string balance;
                cin >> balance;
                match = true;
                bA.m_balance = balance;
                outFile << bA;
            }
            else
            {
                outFile << bA;
            }
        }
    }
    else
    {
        cout << "File cannot be opened \n";
    }
    if(match == false)
    {
        cout << "Name not found \n";
    }
}