Android Contact Management App Development

I am looking for an Android programmer who can create an application to manage the phone numbers of more than 500 workers, meaning that I can quickly search for the person and send him a regular message, WhatsApp message, or via Facebook. The application should not be available to everyone, only to those who have a secret code that allows them to access it. The application specifies the information and data of the person who was searched for, including his photo, name, description, and phone number. The application should be easy to use, beautiful, and attractive in its icons and buttons. should have the following main functionalities:

- Add/Edit/Delete contacts
- Group messaging
- Contact import/export, specifically syncing with other applications

The app needs to be able to sync with Google Contacts and Google Sheets for contact import/export.

Ideal candidates should have:
- Strong experience in Android app development
- Prior experience with contact management apps
- Skills in integrating with Google services
- Proficiency in implementing group messaging features.

Please provide examples of relevant apps you've developed in your proposal.