QGIS materials (Free):
https://www.gislounge.com/free-ways-to-learn-qgis/
https://www.qgis.org/en/site/forusers/trainingmaterial/index.html
https://docs.qgis.org/3.22/en/docs/training_manual/index.html
Postgresql materials (Free):
https://www.postgresql.org/docs/
