SOAP API Trailhead Challange

Hello Trailblazer, 

I am trying to complete the challenge for Apex SOAP Callout unit but to complete that I need to create apex class from WSDL file, but I am unable to open the WSDL file, after clicking on the link of file it shows this site can't provide a secure connection. I am also attaching the screenshot of the window. I have already added the endpoint in Remote Site Setting. Any other workaround would be very helpful.

Thank you in advance.

#Traihead Challenge