Hello.

How do I change the language back to English? Everything on the game is in Brazillian Portuguese, from the lines to voices and even the map.

I'd like to change this to their original voices and art. While it is cool to play on the Brazil map, I would like to play on the original map for the campaign.

Sounds like you downloaded the Brazilian Portuguese installer. In order to download the English one, go to your library: https://www.gog.com/account Click on Stronghold HD and select English in the "Language" menu (see attached screenshot). After that, the installer you'll download will install the game in English (and should have the Britain map in the campaign).