Need API to retrieve data from a sharepoint site and enter into a ticketing system

Hello,

Can anyone provide guidance on how to develop an API to retrieve data stored in a sharepoint site (e.g customer names and product selection will always be changing on a daily basis) and enter this data into a ticketing system. Please provide GET, POST responses and I am sure there will be code that needs to be entered.

THanks,
Needhelp857