I got 2 free xbox 360 games in both different languages...I don't know why

I don't know why anyone thinks this competes with Titanfall. They could not be more different. There is plenty of room for both games! That's why I got it. If you want some variety from Titanfall, you have this! There is no reason to pass on it just because
a different game comes out in 2 weeks. If its a money thing, I understand but both are totally worth it!

I installed the game on 2 different xbox ones and played it with 2 different accounts. both have the same error. Language and country are both configured to German.

Well that would be why I don't think you fully understand how consoles work

Xbox 360 games are region locked

Xbox one are region and language independent

Therefore any xbox 360 game you download will pick the language based on the primary language of your region

Changing language or region will most likely incur a region lock and yes language has to do with compatibility as some games are language specific

Black ops 1-2 halo gears of war are examples of such games

80% of xbox 360 games are region locked and no they aren't labeled other then xbox one or xbox 360 or xbox (for next gen games(

Hello,

Do you have the region set differently in the settings of the Xbox? I wonder if this is causing it to start up in English?

Of course not. All the languages and region are set to italian in both consoles.

Also that would't explain why the game is listed with 2 different file size...

The only folks that can help you are
https://enforcement.xbox.com

They do not monitor support forums. You may be able to request a review