Thank you for your reply. I did follow your instructions but I am still getting the error. Now, funny thing, I cleared the SSL settings in IIS10 and now it does work (see picture). I thought those checks shall be checked for it to work. I was wrong . but I am happy about that since it now redirects to https and the whole site is encrypted, not only the logon screen (which I was been pressed to keep, instead of whole site encryption).
THANK YOU VERY MUCH!!!!