is it now possible to upgrade my Herobook Air 11.6 to windows 11 without problems?
I thought Microsoft will let you upgrade for free, they want everybody to use Win 11 now if your system is compatable. Just make sure you can put Win 10 back when you get to hate 11 
EDIT:
Try this: https://www.microsoft.com/en-gb/windows/windows-11
or this: https://www.microsoft.com/software-download/windows11