It helps to see what FolioPress does with a request before your template ever runs, because it explains why templates are so short.
Two things worth noticing. The language is read from the URL prefix, so /pt-pt/sobre and /about are the same page in two languages, and the context handed to your template is already in the right one — every title, slug, menu label and piece of content. And the template is chosen for you: for a page whose primary-language slug is about, FolioPress looks for page-about.html first and falls back to page.html. There is nothing to wire up.