Hi Kaushik,
I would suggest you to look into this course, to get an idea of what HANA is.
Course: An Introduction to SAP HANA by Dr. Vishal Sikka
Moving further you can choose on what areas you would like to focus.. BW on HANA, HANA XSJS and so on..
HANA ACADEMY covers most of the topics required :
http://www.saphana.com/community/hana-academy/
This OpenSAP course would also help :
Course: Introduction to Software Development on SAP HANA
-Avinash Raju