(2) Are you playing this EUR version of the game on a 3DS system that has JPN or USA firmware?
If you are playing an out-of-region game where the regions between the game and 3DS firmware do not match, you need more than just the (x) Enable game patching. Create and specify the game's per TitleID locale.txt with the appropriate region and language selection.
For example, if I wanted to play Monster Hunter Stories (EUR) in Dutch on my USA n3DSXL, I add this text file to the SD card written with this code.
(3) Are your 3DS firmware and custom firmware up-to-date?
Monster Hunter Stories is compatible on 11.4 firmware or newer.
Some games aren't stable on older versions of Luma3DS.