Open a site, log in and get data with App

I’m making an app and I need to know if this I’m trying to do is possible, I need to open a link from a website, which will open a login screen, and then get the data from the site that opens, with HTTP.get maybe.
First Page Link

I have the login and the password, but I need a function that automatically fill the fields and enter, to enter the next page, without showing to the user of preference. The next page I can get the data with HTTP.get


Normally one would do this server side, so you only have to call 1 URL that does everthing else in the background.