iPhone 6 stuck while updating to iOS 9.0.1

Hello everyone,

My iPhone 6 had some troubles under iOS 9 (worst was I couldn't use Touch ID), and I wasn't able to update to iOS 9.0.1 directly on the phone (an error occurred every time). I decided to do it with iTunes, at exactly the half of the loading (part when checking if the update is in order) iTunes tells me the iPhone is unable to get updated. "an unknown error occurred (53)" as you might see below (in French)

So basically I can't use my phone anymore, can't update it, can't restore it (already tried with recovery mode, without success). And worst part is that my guarantee was up to the 26th September 2015...

What do you think I can do ?

Thanks by advance for your answers and I am sorry if you can't understand everything I wrote, English is not my mother language, feel free to ask me if something is unclear.

Quentin