Redesign and Customize Theme with API

I need comprehensive theme customization and API integration to ensure all functionalities work seamlessly. This includes redesigning the entire theme to improve navigation, usability, visual design, layout, and responsiveness across devices. The redesigned theme must support key features like user registration and login, as well as robust search and filter functionality. The goal is to create a polished, user-friendly experience that aligns with the desired functionality and aesthetic improvements while integrating necessary API connections for enhanced performance.