For my geology diploma project I need to create DEM from topography map my professor gave me to use as a base map. The map is georeferenced. My idea was to draw lines over the izolines of the map, then specify thair elevation and then create DEM. Equidistance of the izolines is 10m. I don't know how to do it or is it even possible in QGIS.
It can be done in QGIS. It's called digitising when you're drawing over a scanned map (image, or raster in GIS terminology).
Check this handy, simple yet accurate tutorial Digitizing Map Data and come back if you run into more questions.