The biggest issue for a perosn who speaks Portugese but is not fluent in English with providing a translation is it's still not going to be a good translation. Simply put, English has so many different meanings for the same word:

Cup: Something you drink out of; A device used to support the testacles of male sports players; the little item that goes in the hole on the green of a golf course; wrapping your hand around a woman's breast (cup the breast with your left hand is an example); Should see more I keep going? So which definition of "cup" are you looking for?

Beyond that, translating a base Dolphin install will take approxiately 13 hours. I know, I've done it and I've paid others to do it. In the end, it comes down to the fact that no 2 sites are the same and what works to translate one site will not necessarily translate another site properly. Modifications to sites create additional language keys that will probably not be in the translated files you receive. This means you have to go translate those ones also by hunting them down.

The best way: Hire someone who fluently speaks English and the language wish to translate it to and have them do the translation for you after your done with all other parts of your site. Until the site is ready to go excluding the translation, you shouldn't even worry about it.