Language override - strategy

My question is:
For example Portuguese language is far away from completness, even Sent and Received are not translated. I have now 250 language strings in the override file and discover more missing string in using the CB. I think I need 100% of the basic language.php and more strings of the plugins language files I will put into the override.
Because I am not a mother tongue in Portuguese I am using different online translators (for cross checking, it is a lot of work), so my translations are not qualified (in the future I will let improve the languages by mother tongue professionals).

But what if a new update of the Portuguese language comes out and overrides my language.php? Do I have to put all English strings from the language.php into the override? If the original Portuguese language update has more strings translated, should I check this (how? do I have to check ALL strings in the langauge.php?) so that I have the updated information also? A little bit complicated ...

(a dream would be to have all European languages 100% translated ...)

Portuguese language file for CB Gallery is nearly not translated. OK, here I have to do all the work for my own, as I said above ...

You can make a copy of language.php and renamed it to override.php then translate every string directly in it if you want. Beyond that you can try contributing to the language project on Transifex. Even if using tools to help translate it's probably better than no translation at all. If you modify language.php and update the language plugin you will lose your changes; always use override.php. All languages except English are a community driven effort so the more people that contribute the better. See the below for details.

www.joomlapolis.com/localization