Eu falo português.
Yo hablo español.
I speak English.
Translating and editing are best when one has a profound understanding of the grammar and inner workings of a language. You see, language doesn't exist in a vacuum, but within a context. That context could be cultural, when talking about advertising or blogging, but it can also be professional, as it is in the case of most technical writing, wether medical, legal or academic. As a linguist, I have lots of expertise in analyzing texts and can easily move between different contexts in order to find the most exacting choice of language.