Responsive Web & Android Flutter App

I need two customer-facing products created side by side. First, a fully responsive website built with clean HTML5, modern CSS (Flexbox/Grid), and vanilla JavaScript. It should load fast on any device, maintain consistent styling across screen sizes, and be easy for me to update later... (Budget: $250 - $750 USD, Jobs: Android, CSS, Flutter, Frontend Development, HTML, HTML5, Mobile App Development, Web Development)