Fix 502 & Speed Issues

My site has begun throwing 502 “Bad Gateway” errors and pages now load painfully slowly. The first signs appeared only recently, right after I made a few server-side tweaks, so I’m confident the root cause lives somewhere in those configuration changes... (Budget: ₹600 - ₹1500 INR, Jobs: Apache, GTmetrix, LAMP, Linux, MySQL, PHP, Redis, Troubleshooting)