Hi,
The key to making your proof-of-concept app work, is the backend database that you will need.
This will manage the user accounts, messages, and notifications.
You don't mention the system that you are considering - perhaps something like Firebase, or Back4App?
I develop apps for iPhone/iPad and Mac, using Xcode and Swift.
You can see some examples of my work, and client reviews of my completed projects, on my Freelancer profile page.
It looks like you may be new to Freelancer? Before starting the project, there should be a clear understanding of the details, the deadline, and the milestone payments.
If you'd like to reply to this message, we can discuss things further, before you make your decision on awarding the project.
Best Regards,
- Rob Dixon.