hello akorx,
please be careful when using the live system. Not only your chosen language will be transfered to the installed system. You can also install packages into the live system as usual (with apt-get update; apt-get install »package«) and theese modifications will also appear in the installed system.
"What you see is what you get" - the installer really moves the current state including the user settings, only some clean-up happens e.g. browser cache is cleared and some "siduction-live"-packages get removed.
greetings
musca