Правильное подключение .h и .cpp файлов

#include <iostream>
#include <chrono>
#include <random>
#include <string>
 
int random(int num)
{
    int seed1 = (int)(std::chrono::system_clock::now().time_since_epoch().count());
 
    std::minstd_rand0 random(seed1);
    int randomResult = random() % num;
    return randomResult;
}
 
int random(int from, int to)
{
    int seed1 = (int)(std::chrono::system_clock::now().time_since_epoch().count());
    std::minstd_rand0 random(seed1);
    int randomResult;
    do {
        randomResult = random() % to;
    } while (randomResult < from);
    randomResult /= 10;
    randomResult *= 10;
    return randomResult;
}
 
bool task1()
{
    int attempt = 0;
    int maxAttempts = 5;
    int price = random(20, 50);
    int money = random(price, 1000);
    double discount = random(2, 90);
    int answer = money / (price - (price * (discount / 100)));
    bool result = false;
 
    std::cout << "You have a " << money << " dollars." << std::endl;
    std::cout << "Notebook costs " << price << " dollars." << std::endl;
    std::cout << "Today the store has a " << discount << "% of discount" << std::endl;
    std::cout << "What is the largest number of such notebooks you can buy?" << std::endl << std::endl;
    int userAnswer;
    do {
        ++attempt;
        std::cout << "Attempt #" << attempt << "\t";
        std::cin >> userAnswer;
        if (userAnswer != answer)
            std::cout << "Incorrect solution. " << maxAttempts - attempt << " Attempts left. Try again!" << std::endl;
        else
        {
            std::cout << "Correct! Good job!" << std::endl << std::endl;
            result = true;
        }
    } while (result == false && attempt != maxAttempts);
    system("pause");
    system("cls");
    return result;
}
 
int main()
{
    int score = 0;
    int toWin = 10;
    do{
        std::cout << std::endl << "Total Score - " << score << std::endl << std::endl;
        std::cout << toWin - score << " attempts left" << std::endl << std::endl;
        if (task1())
            ++score;
        else
            --toWin;
    } while (score != toWin);
    
    std::cout << "You managed to reach " << score << " Points" << std::endl;
    system("pause");
}

#include <iostream>
 
void Foo1();

#include "task1.h"
 
void Foo1()
{
    int a = 2, b = 3;
    std::cout << "Sum = " << a + b << std::endl;
}

#include "task1.h"

#include "main.h"
 
int main()
{
    Foo1();
    std::cin.get();
    return 0;
}

int random(int num);
int random(int from, int to);
bool task1();