Fix 502 bad gateway error for my magento website.

I'm looking for an experienced Freelancer to fix a very frustrating 502 bad gateway error on my Magento website. I'm using Aliyun hosting. I'm unsure if I have any backup files available. Recently, I was upgrading Ubuntu 18.04 and I got kicked out of the install and downgraded. I had to reinstall php and maybe there are other requirements that need reinstalled. All the magento files and database should not have been impacted. I just need my site to show up again as soon as possible. The ideal candidate would be knowledgeable in ubuntu, nginx and Magento. Experience with coding, debugging, and configurating websites in order to solve 502 bad gateway errors is highly preferred. Most importantly, I need someone who can quickly and thoroughly troubleshoot the issue and restore my website's functionality without too much delay or disruption. With any luck, you are the Freelancer for the job!