Create nginx configuration file for your domain.

1- type in terminal this command and remember to replace "your_domain" with your domain like "mawjood.appsiraq.com"
    $ sudo nano /etc/nginx/conf.d/mawjood.appsiraq.com.conf

2- copy and paste this snippet and remember to replace "your_domain" with your own and port "3001"
    server {
        listen 80;
        listen [::]:80;

        index index.html index.htm index.nginx-debian.html;

        server_name your_domain;

        location / {
                proxy_pass http://localhost:3001; #whatever port your app runs on
                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;
        }
    }

3- press ctrl+x to exit then y  to accept edit  then Enter to create file.

4- To make sure that there are no syntax errors in any of your Nginx files, run:
    $ sudo nginx -t

5- restart Nginx to enable your changes
    $ sudo systemctl restart nginx

Generate SSL for your domain

1- type in terminal this command and remember to replace "your_domain" with your own
    $ sudo certbot --nginx -d your_domain