Website Performance Optimization

I need an experienced front-end developer to optimize the performance of an existing HTML/CSS/JS website with a focus on Core Web Vitals, page load speed, and front-end best practices.
The site is fully live, SEO-friendly, and content-rich, but there is room for improvement in performance, especially on mobile devices.
Current Setup
Custom HTML/CSS/JS, no CMS
Uses:
Google Fonts (Oswald, Inter)
Font Awesome / IcoMoon
Swiper slider
Google Tag Manager
JSON-LD structured data (Organization, Product, Video)
Some Images have been converted in WebP but the website is not playing different images from Desktop to Mobile.
Partial lazy-loading implemented
Preloader and animations present
Complex header and navigation
No heavy JS frameworks (React/Vue)
GOALS
We are looking for a developer to:
Improve PageSpeed Insights scores (mobile & desktop)
Optimize Core Web Vitals (LCP, CLS, INP)
Reduce render-blocking resources (CSS/JS)
Improve fir...