The timings for this lesson are reasonably accurate, but will be updated based on experience. I usually get part way through the functions episode in about 6 hours.
The lesson is designed to be taught sequentially, so doesn’t lend itself to skipping sections.
Make sure the font size is large enough:
Preferences > Fonts > Desktop code font
Preferences > Fonts > Desktop text font
On Windows, the default font doesn’t give a clear distinction between the letter l and the number 1. Consolas seems to be a reasonable choice in this regard.