James

WPTranslator plugin allows you to add a widget to your site providing translations in to multiple languages.
If someone visits your site and wants to translate it they can simply click a flag or select a language from the dropdown box to translate the text into their preferred language.
To view the options available activate the plugin and then go to Settings > WPTranslator
We have kept it really simple with just some styling options.
Visit the main website for news and additional information: <a href="http://wptranslator.com/" title="Wordpress Translator" rel="nofollow ugc">WordPress Translator</a>
It is simple to install and you can place a widget anywhere on your site with flags or a drop down box which when clicked translates your site into the language specified.
If you like the plugin please leave a review. Any suggestions or ideas for how we can improve the plugin would be greatly appreciated.
Full list of languages available for translation at <a href="http://wptranslator.com/full-list-of-translation-languages-available/" title="full list of translation languages" rel="nofollow ugc">WordPress Translation Languages</a>

WPTranslator

WPTranslator allows visitors to translate your site into any language

martinjuhasz

Lets you choose your Backend Language for your complete Backend, also if your Frontend is using another Language (including Multisite). 
You can choose from any language you installed. For a list of availible languages, check <a href="https://codex.wordpress.org/WordPress_in_Your_Language" rel="nofollow ugc">“WordPress_in_Your_Language”</a> or create your own files.

One Backend Language

Lets you choose your Backend Language for your complete Backend, also if your Frontend is using another Lang (including Multisite)

WPTranslator vs One Backend Language