Maybe it's not that important but it was confusing to me when following the video: when I go to sideview by pressing Numpad 3 (in video: 4:05) the lines I drew with the annotation tool are just straight lines like in front view. In the video the lines of the annotation tool follow the form of the sphere. I guess I did it the same way: pressing ctrl while drawing the lines and I tested it several times. Maybe it's because I use Blender 3.4 and there were changes how the annotation tool works?
oh wow... this was fast... thank you very much. Following the course I found this out as well and came back to answer my question to avoid that someone like you has the work to do this. So I really appreciate your answer, thank you!