working scenario might need more explanation

[konni-b]

download all relevant zipfiles to a folder downloads in our repo
extract each csv into a folder downloads/extracted

1. make it clearer that participants need to create the downloads folder (and the subfolder extracted if even necessary)
2. data_files = os_sorted(os.listdir('./downloads/extracted/')): maybe explain more what it actually does and that if you only have one file that there is not really something to be sorted :)