Multi-Feature Academy Mobile App Development

I need a comprehensive mobile app for my Karate academy, to be developed for both iOS and Android platforms. The app's primary feature will be student registration, but it should also include a suite of additional features:

Essential Features:
- Student registration

Additional Features:
- Payment integration
- Notification system
- User profiles
- Recurring invoicing
- Membership and subscriptions management
- Auto payment reminders via SMS, WhatsApp, and Email
- Automation
- Events management
- Graduation tracking
- Belt exam records
- Attendance records
- Student private portal

Ideal candidates should have:
- Proven experience in developing mobile apps for both iOS and Android platforms
- Strong background in integrating payment systems
- Familiarity with notification systems and user profile management
- Experience in building automation features within mobile apps
- Knowledge in event management and tracking systems
- Strong UI/UX design skills to ensure a user-friendly interface

Please provide examples of your previous work, particularly any similar projects you have completed.