Create a Windows App to download sections of a website as html pages for offline viewing.

I need a windows App that will download parts of a website into a series of HTML files with an index html file that links to all the pages for offline viewing. The websites are car manufacturer sites and the data is workshop manuals that are behind a paywall, so the app will need to provide the username and password to access the content. I currently have access to an app that does this but I do not have the source code for the app. I need an app that functions exactly like this app. The issue with the app I have is that the developer has tweaked it so it only works for one vehicle profile, so I cannot use the app for any other vehicle. I need an app that I can use for any vehicle on a particular website. The app functions like this - I pay the website for a days access for a particular vehicle's information which is linked to my username - then I enter my username and password for the site into the app, I have to have Chrome browser open and logged in when I run the app and the app downloads all the html files relating to the vehicle I have paid access for to a folder and there is also an "[login to view URL]" file which is like a contents page with hyper links to all the pages. I can send you the app and the example output.