Official Joomla! Documentation
The official Joomla! documentation site is docs.joomla.org. Spend some time there and you will definitely learn something new.
https://docs.joomla.org/
Beginners Guide to Joomla!
May 28, 2015 – Absolute Beginners Guide to Joomla!
https://docs.joomla.org/Portal:Beginners
Frequently Asked Questions: Joomla! FAQ
https://docs.joomla.org/Category:FAQ