How to connect to an unsafe wifi?

[AC Question]

Android 5.1 not rooted
When I try to connect with my smartphone to a wifi in a restaurant that I trust most times it happens the following:
I select the network and tap on connect
A popup appears requesting the login and password but immediately an ad appears followed by a screen in which a lock appears indicating dangerous network. Then I select option to use network as it is. In settings it appears that I am connected but I am not really connected as I could not enter the login and password before. Going backwards with the browser does not help.
How can I in practice introduce my log in & pass so I can connect?

 

[B. Diddy]

Welcome to Android Central! This happens to me from time to time as well (especially with Safeway's wi-fi hotspots), and I'm not sure if there's an easy way around it. It probably has more to do with the public wi-fi's settings than with the phone.

What happens if you open your browser and try to go to any website? Do you get the login screen there?