Restore WordPress Site Ownership Error

My site, www.newrattanagency.com, went offline right after I tried to move full WordPress ownership from my previous developer to myself and ran one last plugin/theme update. Since then the front-end shows only an error page—nothing loads.

I need someone who can jump in, trace the exact cause of the crash, bring the site back online, and make sure the admin area is fully under my control. I’m based in Madurai and would prefer working with a fellow Tamil Nadu professional or a local startup so communication is quick and clear, but if you can solve the problem efficiently and honestly, I’m open to talking.

Key outcomes I expect:
• The website loads normally on all devices and browsers.
• I can log in as the sole administrator, with no leftover developer accounts.
• Any plugin or theme that caused the failure is either fixed, rolled back, or safely replaced without breaking the design.
• A brief hand-over note explaining what you changed so I can avoid the same issue next time.

I’ll supply hosting and WordPress credentials once we agree to proceed. Looking forward to getting back online soon.