You can't get everything to know about Magento for free from one place but you can search through the various site. Here are the sites I would recommend

Basic Module

Source 2

devdocs magento

belvg

toptal

You can't get everything to know about Magento for free from one place but you can search through the various site. Here are the sites I would recommend

magento-2-create-basic-module-part-1 by qaisarsatti

rakeshjesadiya blog

All Video Tutorials - devdocs magento

magento2-tutorial for certification

magento-2-tutorial-building-a-complete-module