Hi,
It will take some decent java scripting to complete. As you will most likely need a data source to pull from that has the EN/GER words and definitions.
Just off the top of my head I would first implement a JQueryUI autocomplete on the search text box:
http://jqueryui.com/autocomplete/
Then I would expand on that to use the selection to fill in the words and definitions for each language.
Again, it won’t be the easiest of tasks.