WordPress Lightbox Image Gallery -- 2

My WordPress site is ready for a visual upgrade: I want a clean, responsive lightbox gallery populated with well over 20 images that I will supply. Each image must appear in the appropriate category so visitors can quickly filter through the content.

Here is what I need from you:
• Select, install, and configure a reliable lightbox solution (for example → Fancybox, Lightbox2, or Envira Gallery—whatever integrates best with my current theme).
• Upload and compress the images I’ll provide, assign them to their respective categories, and ensure alt-text is preserved.
• Match the lightbox styling—fonts, colors, navigation arrows—to the rest of the site so it looks native.
• Test on mobile, tablet, and desktop to confirm smooth transitions, swipe support, and quick load times.

Once everything looks and performs flawlessly, send me a short hand-off note outlining how to update or add new categories myself.