Custom Notification System for WP/Next.js

I'm looking for an experienced developer to implement a robust notification system and improve mobile responsiveness for my WordPress and Next.js application.

Notification Requirements:
- Notifications to be displayed on a dedicated website notifications bar and sent to users via email.
- Users should be able to customize what alerts they receive, at least to some degree.

Essential Notifications:
- When a certain demand is posted based on a category
- When a new proposal is received
- When a proposal is accepted, rejected, or completed

Mobile Responsiveness:
- Ensure the site is fully functional and visually appealing on mobile devices.

Ideal Skills and Experience:
- Proficiency in WordPress and Next.js
- Strong knowledge of PHP
- Experience with building customizable notification systems
- Frontend and backend development skills
- Expertise in mobile responsiveness and UI/UX design

Please provide samples of previous work related to notifications and mobile responsiveness. Looking forward to your proposals!