nginx 502 bad gateway with nodejs

Question

i am an student who is working on a nodejs + nginx project taht i didn't start, so im not sure what is going on.... when i try accessing to my website, i am recibing a 502 Bad Gateway nginx/1.12.2 error.

i have been trying to solve it with the answers of other similar question but the problem is still there, i think there is something wrong with the configuration, but im not sure what it is.

the nginx.conf file is as follow

#!/usr/bin/env node
'use strict';
/**
* Module dependencies.
*/

//var http = require('http');
var app = require('../app/app');
var config = require('../config/config');

/**
 * Get port from environment and store in Express.
*/
process.env.PORT = config.port;
var port = normalizePort(process.env.PORT);
//app.set('port', port);
app.listen(port , function () {
console.log('App listening on port ' + process.env.PORT);
});
/**
 * Create HTTP server.
 */
//var server = http.createServer(app);

/**
 * Listen on provided port, on all network interfaces.
 */

//server.listen(port);
//server.on('error', onError);
//server.on('listening', onListening);

/**
 * Normalize a port into a number, string, or false.
 */
function normalizePort(val) {
    var port = parseInt(val, 10);
    if (isNaN(port)) {
        // named pipe
        return val;
    }
    if (port >= 0) {
        // port number
        return port;
    }
    return false;
}

/**
 * Event listener for HTTP server "error" event.
 */
/* function onError(error) {
    if (error.syscall !== 'listen') {
        throw error;
    }
    var bind = typeof port === 'string'
        ? 'Pipe ' + port
        : 'Port ' + port;
    // handle specific listen errors with friendly messages
    switch (error.code) {
        case 'EACCES':
            console.error(bind + ' requires elevated privileges');
            process.exit(1);
            break;
        case 'EADDRINUSE':
            console.error(bind + ' is already in use');
            process.exit(1);
            break;
        default:
            throw error;
    }
} */

/**
 * Event listener for HTTP server "listening" event.
 */
/* function onListening() {
    var addr = server.address();
    var bind = typeof addr === 'string'
        ? 'pipe ' + addr
        : 'port ' + addr.port;
    console.log('Express server listening on port: %d, in %s mode', 
app.get('port'), app.get('env'));
} */

also i have already checked the logs

2018/11/26 09:32:14 [error] 974#0: *7094 connect() failed (111: Connection 
refused) while connecting to upstream, client: 189.183.151.200, server: 
mexcx, request: "GET / HTTP/1.1", upstream: "http://127.0.0.1:5001/", host: 
"67.227.198.57"

hope you can help me on understanding what is going on, cause at the beginig it was working just fine, i was doing some changes on the code, i restart the server and i got the problem