I am new to Nginx and Ubuntu 16.04.
I had an Nginx website up at armadasol.com with a NodeJS script. It uses a local MongoDB and PM2. I made some hard code changes on my home page and after I refreshed the website in the browser, the changes did not update. I restarted my server and now I get a 502 Bad Gateway error.

I have got the PM2 restarted.
MongoDB is restarted

I use Nginx, NVM, NodeJs, MongoDB, PM2.

My nginx.conf server settings:

user www-data;
worker_processes auto;
pid /run/nginx.pid;

events {
    worker_connections 768;
    # multi_accept on;
}

http {

      server {
   listen         80 default_server;
   listen         [::]:80 default_server;
   server_name    localhost;
   root           /usr/share/nginx/html;
   location / {
       proxy_pass http://127.0.0.1:3000;
       proxy_http_version 1.1;
       proxy_set_header Upgrade $http_upgrade;
       proxy_set_header Connection 'upgrade';
       proxy_set_header Host $host;
       proxy_cache_bypass $http_upgrade;
   }
}

    ##
    # Basic Settings
    ##

    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    keepalive_timeout 65;
    types_hash_max_size 2048;
    # server_tokens off;

    # server_names_hash_bucket_size 64;
    # server_name_in_redirect off;

    include /etc/nginx/mime.types;
    default_type application/octet-stream;

    ##
    # SSL Settings
    ##

    ssl_protocols TLSv1 TLSv1.1 TLSv1.2; # Dropping SSLv3, ref: POODLE
    ssl_prefer_server_ciphers on;

    ##
    # Logging Settings
    ##

    access_log /var/log/nginx/access.log;
    error_log /var/log/nginx/error.log;

    ##
    # Gzip Settings
    ##

    gzip on;
    gzip_disable "msie6";

    # gzip_vary on;
    # gzip_proxied any;
    # gzip_comp_level 6;
    # gzip_buffers 16 8k;
    # gzip_http_version 1.1;
    # gzip_types text/plain text/css application/json application/javascript text/xml application/xml application/xml+rss text/javascript;

    ##
    # Virtual Host Configs
    ##

    include /etc/nginx/conf.d/*.conf;
    include /etc/nginx/sites-enabled/*;
}

Question 1) Why am I receiving a 502 error?
Question 2) How do I prevent this next time I make changes in my files?
Question 3) Is there a script anyone recommends that can restart my nodejs app when I make changes.