A wealth of material exists for learning both mapping in OpenStreetMaps OSM and QGIS. A few of the many sources are listed below. An online search for "learning OSM" or "learning QGIS" will bring up links to a number of sites.
OpenStreetMap Tools-- HumanitarianOpenStreetMap Team (HOT)
provides links to a number of tools for learning mapping and working
in OpenStreetMaps at https://www.hotosm.org/tools-and-data
OSM Training-- OSM training material is also available ast https://learnosm.org/en/.
Beginning OSM Mapping--Material for beginning mappers is available at https://learnosm.org/en/beginner/start-osm/
Youtube-- Searching "youtube qgis osm" on a browser will bring up a number of hits on loading OSM data into QGIS. Searching for "youtube beginning qgis" also brings up numerous hits.
QGIS Training Manual-- A training manual provided by QGIS is available at https://docs.qgis.org/3.16/en/docs/