we are at the verge of going into the last phase before the next release of ~friendica. If you happen to speak English and a second language and furthermore feel qualified enough to translate text from EN to that other language, we could use your help!
Translation of Friendica is done at Transifex (mostly) where you can use an online editor to translate the original strings into other languages. You need a (free) account at Transifex and then you can join the translation teams to work together on the translations.
The most important file to be translated is the messages.po file, it contains the strings to be translated from the core of Friendica. There are many other files to be translated as well, they belong to the Addons, the git repository and the directory, but they are not that important. E.g. we use the translation progress of the core messages.po file as proxy to determine if the translation should be included in the repository.
Anyhow, translation of the addon files might be a bit more satisfactory, as there the progress is more visible ;-)
In the editor of Transifex, you can simply select the untranslated strings to focus them. You can also search for already translated strings, if you are unhappy with the translation.
If you do the work at Transifex, I will update the Friendica repository periodically with the results of your work. Thanks a lot in advance <3 :-D
As an alternative to use Transifex, you also could use any other translation tool that supports the PO format. The base file can be found in the Friendica sources at /view/lang/C/messages.po if your target language does not already have a separate directory that contains the translation. If you choose that way, please send the messages.po file via mail to me, especially if the language is not included in the repository so far. Or, if it is, you could also make a pull request with your updates.