Windows 10 modern-ui apps wrong language

I've solved my problem by putting in the languages settings the French language at the top. After some restarts all my modern ui apps are in French.

Registered just to post this, hope it helps others who got fustrated with it as well.

Under Control Panel > Language > Advanced Settings > Override for Windows display language

Defaults follows your language setup, you can choose to select what language you wan't to show here.

It's a late answer, but when I had the same problem I solved it very quickly and easily. I live in Germany and love my OS to be in English. In order to achieve a full English OS, including apps, and a German keyboard layout I went into my locale settings (Settings => Time & Language => Region & Language) and first off moved English (which was set to override the OS language) to the top. Then I clicked on English, clicked on Options and directly clicked on Add a keyboard and selected the German keyboard layout. After that was set I removed the US keyboard layout and then had Windows 10 displaying in English, including all of the apps, with a German keyboard layout.

I hope this answer alone might help or would give you some options to look after.