Varnish configuration and 502 503 errors

I am looking for an experienced freelancer to assist me with my Varnish configuration and 502 503 errors. I am running my website on a cloud hosting environment, and I get between 100-1,000 visitors per day. Currently, I do not have any documentation related to the web server and Varnish configuration and I will need assistance creating it. The freelancer I am looking for will be highly experienced with Varnish configuration and error fixing/troubleshooting.