Introduction to GIS: https://docs.qgis.org/testing/en/docs/gentle_gis_introduction/

QGIS Website : https://qgis.org/en/site/

Download QGIS stable version (https://qgis.org/downloads/QGIS-OSGeo4W-3.4.13-1-Setup-x86_64.exe)

Download latest version https://qgis.org/downloads/QGIS-OSGeo4W-3.10.0-1-Setup-x86_64.exe

Download and Installation of QGIS version 2.18 https://spoken-tutorial.org/watch/QGIS/Installation+of+QGIS/English/

User Guide/Manual:  https://docs.qgis.org/2.18/pdf/en/QGIS-2.18-UserGuide-en.pdf

Spoken Tutorials: https://spoken-tutorial.org/tutorial-search/?search_foss=QGIS&search_language=English