"Progressbar" (with blue boxes)
It should be an <ol> with ahref="#", inside a <nav>
A list-item must have an aria-label with the slide title, tooltip is displayed
"Has task" and "Answered task" should also be announced to screen reader
It can be navigated by keyboard keys (test in NVDA and use role="application", it needs to be in the correct role for keyboard to be activated)
The currently opened page should be announced
Summary slide should be an internal link as well but rel:"no-follow"
Navigation is accessible according to the description