Car Hire Site PHP Repair

My car-hire website was originally hosted on iPage but Network Solutions now controls the server. Since the move the entire site has gone offline, throwing a “trying to read property…” PHP error any time a page is requested. I need someone to:

• Upgrade the site to a stable, supported PHP version that works on Network Solutions.
• Resolve the current runtime error so every page loads correctly and the booking form functions again.
• Bring the theme up to date—or, if that proves inefficient, recommend and install a comparable modern theme that keeps the look professional and responsive.

Once you’re done the site should load quickly, all pages and forms must work end-to-end, and there should be no visible PHP warnings. A short hand-over note outlining the changes and any follow-up steps will complete the job.