TO THE OP:
You'll find a form at this site:
http://ec.europa.eu/transport/passen...ts_form_en.pdf
You print it and fill it out and first send it to Lufthansa. Give them about 6 weeks to respond, then send the form to the enforcement authority in Germany. You'll find the address of the enforcement authorities in all EU countries through a link on the form
In the EU delays due to mechanical problems are considered the responsibility of the airline for which compensation is due since the case of
Wallentin-Hermann