"Sport is not always a game."
Translation:Спорт не всегда игра.
Also a native English speaker, and this sentence is nonsense in this context. Almost certainly, the course designers mixed up the irregular uncountable "sports" (the collection of athletic competitions, usually with teams and some kind of ball) and the regular singular "sport" (one of such things). As such, this sentence requires an article, "A sport is not always a game", or to use the actual uncountable, "Sports is not always a game".
Unfortunately, when "sport" is used uncountably like in the given sentence, it refers to shooting things for fun (actually, for any reason other than eating what you shoot). So, this sentence has meaning, but that meaning is, "shooting things other than hunting is not always a game", which is probably not what they intended given the context of this lesson. Also, it's kinda dark.