MERN Stack Developer Needed for Project Refinement

I'm in need of a proficient MERN stack developer to address a number of issues in my existing project, and to further refine its functionality.

Key Tasks:
- Resolve current errors, slow performance, and UI/UX issues.
- Update and fix the existing functionalities in Node.js.
- Tackle other functionality errors and database issues.

Specific Requirements:
- Solve issues with user authentication and data validation.

Ideal Skills and Experience:
- Proven expertise in MERN stack development.
- Extensive experience in fixing and refining projects.
- Strong understanding of Node.js, React.js and MongoDB.
- Familiarity with user authentication and data validation.
- Excellent problem solving and analytical skills.