It is highly recommended that you download the files one at a time and allow them to fully download before you attempt to open them.
Tutorial videos can be very large, so even if you have a fast internet connection, it may take some time to complete each download.
Always download to a computer first and then sync to your various mobile devices from your copy on the computer if you intend to access them on the go.
When you click the links to download the files, you may get an option to either ‘Open’ or ‘Save’ these files. Please select ‘Save’ and not ‘Open’. If you selected ‘Open,’ it will store the file in a temporary location and it will be gone once you close the window and a further download will be required.