Arindam,
I would say it might be tough to learn SAP SD on your own. There are some SAP jargon which you might not understand right away.
I was in your position some years back, I enrolled in an (unauthorized) online SAP SD training, after that it was much easier to do self study and dive deeper into each topic.
Search the internet and get enrolled in an online SAP SD course. For selecting the proper course, you can ask for free demo sessions.
TW