Education App Repair or Rebuild

I need an experienced mobile app developer to either fix my malfunctioning education app or build a new one if the price is reasonable. The app is currently available on both iOS and Android platforms.

The current app has numerous issues:
- App crashes frequently
- Features not working as intended
- Poor performance or slow response

Ideal skills and experience:
- Proven track record in developing and maintaining mobile apps, particularly in the education sector.
- Strong problem-solving skills to diagnose and fix existing issues.
- Proficiency in both iOS and Android development.
- Ability to deliver a smooth, user-friendly experience.

If you can provide a detailed estimate of effort and cost, that would be appreciated.