React Developer for Educational Quiz App

I'm in need of a skilled React Developer to create an educational quiz application primarily featuring multiple choice questions. Although the level of complexity of the questions was not specified, one should be ready for a varied range.

The successful bidder must possess:
* Advanced knowledge and experience in React (JavaScript Library).
* Solid experience in mobile app development and design.
* A proven track record in creating interactive quiz apps is preferred.
* Excellent troubleshooting and problem-solving abilities.

Your duties will include:
* Developing and implementing a responsive interface and smooth functioning for the quiz app.
* Ensuring the quiz app has a user-friendly design and easy navigation.
* Integrating the app with a database to store all the quiz questions and user answers.
* Implementing a point or scoring system to grade the users' applications and providing immediate feedback.
* Adhering to good coding practices and standards for easy maintenance and future upgrades.

I look forward to your innovative ideas. Please provide a portfolio or examples of similar work completed.