Backend Fixes, Updates and Integrations Needed

I have built a project using Loveable AI and now need some error fixing and some updates and integrations. It's built on frontend and backend React_shadcn TS and Supabase database.

I am encountering several backend issues that need addressing:
- Authentication problems
- Routing issues
- Some updates of key functions

Additionally, I am looking to implement:
- New features
- Third-party service integration
- Performance improvements

Ideal candidates for this project should have:
- Extensive experience with React and Supabase
- Strong backend development skills
- Prior experience with integrating third-party services
- Ability to work on performance improvements