I need someone to fix Error 502 Bad Gateway nginx/0.7.67 on my website

I need someone to fix the error mentioned. It should be fairly simple and I could probably do it myself if I follow procedures correctly but I would prefer someone with a lot more knowledge and experience than me.

I've set £15 but please disregard and send me your realistic bids so we can agree on a good deal.

The url is www.kiqlist.com (currently set to private and you would need a username and password to access it).

My server is Linode.


Thank you and best regards.