How do I correctly declare my if or while statement to meet the desired input?

Okay so I am still way of a beginner at c++. I have been attempting to code a decent basic calculator in order to test my basics and what I know. I can not for the life of me understand why the program does not restart through loop and just continues to end every time, whether I input "Yes", "yes", "Y", or "y". Here is what I have:

#include <iostream>

using namespace std;

int main()
{
    int a, b;
    string c, d;

    while(c != "+", "-", "*", "/" or c == "Yes", "yes", "Y", "y") {

    cout << "N1 = ";    cin >> a;   cout << endl;
    if(!cin)//If anything but integer given, program ends
    {
        cout << "Give a Number next time.. " << endl;
        return 0;
    }

    cout << "N2 = ";    cin >> b;   cout << endl;
    if(!cin)
    {
        cout << "Give a Number next time.. " << endl;
        return 0;
    }
    cout << "+ , - , * or / ? ";   cin >> c;   cout << endl;
    if(!cin)
    {
        cout << "Give a Number next time.. " << endl;
        return 0;
    }

    if( c == "+")//Operator Functions from input
    {
        cout << a + b << endl;
    }
    else if( c == "-")
    {
        cout << a - b << endl;
    }
    else if( c == "*")
    {
        cout << a * b << endl;
    }
    else if( c == "/")
    {
        cout << a / b << endl;
    }

    if(c != "+ , -, * , /")//if not operator, Try again?
    {
        cout << "Again?... Y/N? " << endl;
        cin >> c;
    }

    if(c == "Yes", "yes", "Y", "y")
    {
        cout << "Restarting.. " << endl;
    }

    while(c == "No", "no", "N", "n")
    {
        cout << "closing... " << endl;
        return 0;
    }
}

I have also tried changing the very last while to an if statement but neither works. Just hoping to see what I am misunderstanding. Thanks! Maybe even some tips to shorten my code or make it simpler would be much obliged as well!