Louy Alakkad

This plugin gives you the ability to run the site in a language (Arabic for example) and use the admin panel in another (like English).
Just go to Settings » General and choose your language.

Admin Locale

This plugin allows you to change the language of the admin panel without changing the whole site language.

jomo

Adds Translate button to the WordPress admin bar to translate any selected text. 
Adds Translate buttons to BuddyPress and bbPress messages.
Translate translates selected text to current locale: where user is logged in, this is the user’s preferred language.
Perfect for a multilingual Buddypress site, this tool allows your users to translate messages to their own language.
Other tools translate the whole site but a polyglots and language learners may not want this, for learning it is best to see the original, and translate only where necessary. 
Or the whole site may be already translated to your preferred language but you are getting messages from other users (or from some untranslated plugin) and you want to translate those.
Currently uses Google Translate.
<h3>Contribution</h3>
If you have a feature request, or if you have developed the feature already, please feel free to use the <a href="https://github.com/Jon007/jm-buddy-translate/issues" rel="nofollow ugc">Issues</a> and/or (Pull Requests)[https://github.com/Jon007/jm-buddy-translate/pulls] section.
Plugin translations are provided for English, French, Spanish, Chinese, please feel to contribute more <a href="https://translate.wordpress.org/projects/wp-plugins/jm-buddy-translate" rel="nofollow ugc">translations</a>.

JM Buddy Translate

Quick and easy translate BuddyPress and bbPress messages or any selected text.

Admin Locale vs JM Buddy Translate