Urgent Joomla Homepage Fix

My Joomla site (currently on 5.3.3) has slipped into the dreaded “white page” state and I need to bring it back to life, fully updated, within the next 48 hours. Here is the ground-zero checklist I want you to work through with me:

• Troubleshoot the blank front-end, using my existing backups if a clean restore is the quickest route.
• Confirm that an update to Joomla 5.4.8 is safe; proceed only if SP Page Builder and SP Eventum remain fully functional afterward.
• Update both extensions—I have an active JoomShaper licence ready for SP Page Builder—and catch any core or third-party patches we have missed.
• Verify server-side compatibility (PHP version, database, etc.) so we do not run into hidden conflicts.
• Clear the lingering Joomla notifications once everything is stable.
Site is hosted on Bluehost if that matters

No new features are required; I’m after a reliable, technically sound base so I can start adding fresh conference content myself. I’ll stay available for credentials, backup archives, and quick answers while you work, but I’d like the heavy lifting handled by you. Deliver back a site that loads correctly, reports no update warnings, and leaves me confident the platform is current and healthy.