I, sadly, did not like the language mixing. For one thing, Jacques is the french equivalent of Jack, if you were Jack, you wouldn’t go to france and suddenly start introducing yourself as Jacques. Also, I may be able to speak french quite well, but not german. it relies on me speaking three specific languages. The language phasingf also gave a disjointed feel.
The slow phasing into french was alluded to in a french bit (un changement graduel – a gradual change) and was meant to show they changed the timeline to make everything french from the napoleonic era forwards. Because of this Jack’s parents (in this new timeline) named him the french equivalent as everything is different but no-one notices the changes.
In contrast the abrupt switch to german is a reference to the many MANY time travelling themes in film where someone tries to kill Hitler, travels forward in time and everythings German. Again alluded to in the German part (Das war immer gearbeitet in den Filmen – That’s how it worked in the films).