Update to a 10 year old reader app

I have an (local) html based book reader app. It's been 10 years since we published an update. Because my beloved, freelancer coder has passed away. App was working until ios 12 though. Now I want to re-publish it. Even though it is an ebook reader, there are some funny feautures that needs to be checked.

Project Description: Update to a 10 year old reader app

Operating System: iOS

Updates Required: Bug Fixes

Deadline: Within a month

Skills and Experience:
- Experience in iOS app development
- Proficiency in bug fixing and troubleshooting
- Strong knowledge of app interface and user experience
- Ability to work within a specified deadline