Featured image size on single post

Hi!

I have a couple of questions I’m hoping someone can help me with.

First –

I’ve set up the code to use featured images automatically on single posts pages, which works amazing. Now, is there a way to make the picture touch the up and side margins of the post layout?

Here’s what it looks like: https://mychristina.com.br/2016/08/09/telepathy-nova-musica-de-christina-foi-escrita-por-sia-e-stargate/

The post layout is boxed, but if there is a way to allow the image size to go bigger and actually touch the margins of the layout, that would be perfect!

The second question is about the post navigation text. There’s a translation mistake in Brazilian portuguese, is there any way I can change it?