Senior WordPress Developer: Legacy Code

I have a nature photography website, engage-the-exotic.com. The site is fully functional, and the visual design is strictly established. I do not want to change the aesthetic.
However, the underlying code is legacy (hardcoded widths, inefficient queries) and needs to be modernized to fix "Mobile-First" indexing issues, eliminate server timeouts, and meet 2025 coding standards.
Primary Goal: Transform a desktop-only legacy site into a fast, mobile-responsive site to recover SEO rankings, without altering the desktop visual experience.
Site Structure & Scope Details
Photo Pages (1,000+): These all use one single template and share a consistent 995px width. You do not need to edit 1,000 pages individually; a global template fix is expected.
Home Page: Unique but basic layout containing multiple sliders.
Barranquilla Carnival Pages (4 pages): These have unique, custom layouts distinct from the main template and will require manual refactoring.
Site Map: Basic XML sitemap that automatically updates when a new photo page is added. This functionality must be preserved.
Scope of Work
1. Critical Speed & Stability (The "504" Fix)
The Issue: The current template uses a legacy database query (get_posts with 'numberposts' => 500000) to generate "Next/Previous" navigation. This occasionally causes 504 Gateway Timeouts.
The Task: Replace this legacy loop with standard, efficient WordPress logic or optimized SQL.
2. Code Modernization (CSS & Responsive Layout)
Fluid Layout: Refactor hardcoded pixel widths (specifically the 995px containers) to modern, fluid CSS (e.g., max-width: 995px; width: 100%).
Mobile-First Indexing: Ensure the site passes Google's "Mobile-Friendly" test. The site must be natively responsive on all devices while maintaining the exact desktop look.
Font Size: Update body font size to a modern standard (minimum 16px) for readability without breaking layout headers.
Contact Form: Ensure the Contact Page's form container (.wrap-contact) is fluidly responsive on mobile.
3. AI Readiness & Dynamic Schema
The Task: Implement Dynamic JSON-LD Schema (Structured Data) to accurately label content for AI engines and Google Images.
Conditional Logic Required:
Exotic Plants/Animals Pages: Apply Species or BioChemEntity schema.
Vistas Pages: Apply Place, ImageObject, or Article schema.
4. Code Hygiene
Debug Output: Disable/Hide the raw debug text currently visible from the legacy "Simple Fields" plugin.
Navigation: Preserve the existing keyboard navigation (Left/Right arrow keys).
Contact Form Logic: Ensure the existing logic that passes the species name/slug to the contact email is preserved during refactoring.
5. Photography & Asset Optimization
Homepage Sliders (Critical): The homepage contains ~15 sliders. These must be optimized to prevent mobile crashing while maintaining the visual experience.
Auto-Play Logic: Sliders should cycle automatically (Auto-Play) but must Pause on Hover.
Smart Loading: Implement logic so that hidden slides do not load until they are about to be displayed.
High-Fidelity Compression: Perform a Bulk Optimization on the Media Library to generate WebP versions.
Quality Standard: Strict adherence to "Lossless" or "High Quality/Glossy" compression settings. Do NOT use aggressive/lossy compression. The visual sharpness of nature photography must be preserved.
Safety: Ensure the process is non-destructive (original files must be preserved on the server).
Lazy Loading: Implement native loading="lazy" attributes on all images.
6. Caching & Housekeeping
Minification: Minify CSS and JavaScript files to reduce payload size. (Note: Only "combine" files if it does not break legacy functionality).
Caching: Configure server-level caching or a standard plugin and ensure Browser Caching is active for static assets.
Cleanup: Remove unused plugins and legacy themes to reduce security risks.
Requirements
Staging Environment: Work must be done on a staging site/copy, not the live site.
Expert knowledge of WordPress Performance Optimization (Database & Caching).
Experience with Schema Markup and modern front-end refactoring (CSS/HTML).
Constraint: The site’s visual "Look and Feel" must remain unchanged on desktop.
Timeline & Availability
Start Date: IMMEDIATE. I want to start as soon as possible.
Estimated completion time.
I am open to technical suggestions for improving speed and stability.
Application Questions (Required)
Please answer these 3 technical questions in your proposal so I can verify your approach:
Regarding the "Simple Fields" plugin mentioned in the scope: Since this plugin is outdated, what is your specific technical plan to handle the data currently stored in it?
For the "504 Timeout" issue on the Next/Previous buttons: Instead of the current get_posts loop, which specific WordPress function or SQL approach would you implement to fix the speed issue?
For the "AI Readiness" task: Which specific Schema.org types would you assign to the "Rare Flower" pages versus the "Landscape/Vista" pages to maximize SEO?
 
 ... Show more