SAP S/4HANA Structure for Developer

[HadiR]

I am new to SAP, learning ABAP development and working in SD Moule.
Are there Courses or Documents that help to understand SAP system from the Developer's point of view?
Where I can understand the flow of the data and code, learn the best practices, restrictions functions, etc.
Learn about implementing Extensions, Enhancements, Amendments, and Exist.
Also learn about extending or enhancing Fiori Launchpad Apps.
BAPI, ALV, etc.

[raymond_giuseppi]

There are many such documents use search tools.

(Your question is much too vague or too broad for a simple answer 😉)

[HadiR]

I agree with you, thats beacuse I am a biggener I did ABAP Core Skills Certificatation.

but still, I don't understand the SAP system landscape code wise. and I am looking for something detailed explains the system itself, not ABAP programing language.