I recommend you check out the tutorial titled "Fundamentals API - Company Tearsheet Estimate", which provides general methodology for data retrieval using Eikon Data APIs, how to go about metadata discovery (finding field names and parameters) and provides examples of fundamental data retrieval. You may also want to check out the following articles:
For ESG data retrieval: "How to integrate ESG data into investment decisions". For fundamental data retrieval: "Working with Fundamental and Estimates Data - A DCF Example", "Economic Value Added".