Android App Code Review

I need a thorough review of my Android app code, focusing on:

- Security issues
- Optimization
- Device-specific issues, especially on older Android versions (Lollipop and up)

Ideal Skills and Experience:
- Expertise in Android development
- Experience with security best practices
- Familiarity with older Android versions and common issues
- Strong optimization skills

Please provide a detailed report on any identified issues and recommendations for improvements.