Registered letter received, risk of contravention of characterized negligence.

I just received this registered letter this morning, informing me that I risk criminal prosecution before the police court, and a fine of €1500, and that I need to respond to a one-page questionnaire. What am I really risking? Considering these articles from Numerama, where the questionnaire is exactly the one I received, https://www.numerama.com/magazine/31093-hadopi-le-questionnaire-qui-peut-vous-pieger.html published by Guillaume Champeau on October 28, 2014, and the one from 2011, https://www.numerama.com/magazine/20964-devant-l-hadopi-le-silence-est-la-meilleure-des-defenses.html, it is said that the best defense is silence? What do you think?
Note that I have already been subject to a first graduated response, which was closed in 2012, because I avoided downloading for six months, and now they say that I have received two recommendations since 2013, and that the last one, which is the third, was recorded in January 2015...

They say that the rights commission will examine my case with a view to its "possible" transmission to the public prosecutor...

I have 15 days to submit my observations, but is this a good thing? If so, what should I respond to counter their letter? And should I even respond to them?

Thank you for your quick help!! Best regards... you can contact me by private message, it might be better..?