Looking for an embedded firmware developer -- 2

We're building a library for network communication. This job involves building AT commands interface for microcontrollers to communicate with network modules. The library should be hardware-independent and written in C++17. See attached file for more details.
I attached some code files to give you a better idea about the job. Please find it in the attachments.
You can find details in README.md.
Please provide me with:
1- Your suggested approach for implementation (very briefly). How the library would be structured.
2- Your estimated time for completion.