.NET Core 2.0 (Preview) HTTPS core error

So, I installed VS2017 v15.3 to try out the new .NET Core 2.0. Created a new project "Web Application" with the possibility of individual authentication. Launched the project, registered.

Everything seems fine now, but then I tried to create a new class for my database, tried to add a migration and then I got the message:

Unable to configure HTTPS endpoint. For HTTPS setup see https://go.microsoft.com/fwlink/?linkid=848054

So, I followed the steps in the documentation, but no positive results. I found out that IIS was not installed on my computer, so I added this feature on Windows, so I can import the certificate as per the doc. - but that doesn't work either.

I'm m not new in VS, but I

not very familiar with configuration options. Currently I have managed to screw things up somehow and even in a new project by pressing Ctrl + F5 under IIS Express I just get the error "This site cannot be reached".

Any advice please?
Thanks to