You will need to install a user script manager extension to install this script.
This script is intended for use only on ProjectEuler.net and it was build to be used together with Firefox's GreaseMonkey extension.
Repository is hosted here: https://github.com/SoboLAN/projecteuler-translation-script
It places 5 flags (British, Romanian, Russian, Korean and German) on top of every problem's page. By clicking on the flag, the corresponding translation of a problem is retrieved.
Obviously, not at all problems are available in the above mentioned languages. In this case, clicking on the flag will do nothing.
Notes about implementation:
The translations are parsed from the corresponding translations websites:
You can see a demo on how the script works in the video on this page: http://projecteuler.radumurzea.net/greasemonkey.php