Board Game Arena

turn
in the current games tab in the top right menu, the text "turn" after player names cannot be translated.
this is not even good grammar in English, missing the genitive suffix on the name. now it's "Name turn", it should be "Name's turn".
of course the genitive must be a separate string, for when there are multiple players in turn. "Name's, Name's … turn".

achievements
on the Your Achievements page, the text "nn achievements" under the game name cannot be translated.

First game on BGA
on the Games in Progress-page, the text "First game on BGA" (when one of the players is newly registered on BGA) cannot be translated.

Countries
in player profiles. I mean, languages are translated, but countries are not…

Dunno about those, but I didn't find "Try to prevent same players to be opponent twice" either
in the tournament creation screen -- probably swiss system