The suggested English translation, 'There is a big square', is weird. Better would be:
1. A big square is there.
2. There is a big square there.
I think #2 is the best English translation, using one 'there' for location (ott) and the other for the idiomatic English filler word.
And note that in #2 it is definitely the second 'there' that translates the 'ott', not the first. That's part of the reason that the DL suggested translation sounds odd.
"Large" is consistently not accepted. I've reported it, but maybe I'm missing if there's a reason why "big" is insisted upon?
One time I wrote large, and it corrected it as big, then the very next sentence used 'nagy' again so I wrote big, and it corrected it as large. Very frustrating.
I think it is just random depending on how they wrote the english translation, so we should just keep reporting them until they all accept both options.
No reason. I suppose there may be some very isolated cases where one sounds much better than the other, but in general, both "big" and "large" should be accepted. In every case I see "nagy" in a sentence, I try both "big" and "large", and report it when either is not accepted. I recommend that everyone does the same.
Remember that this is still an early Beta release of the course, only out a couple of weeks ... there are going to be many mistakes like this, and the developers want our feedback.
No, in Hungarian the word order is much more defined than it is in English. Your sentence just doesn't sound good.
Some nouns will have their (last) vowel shortened in plural: víz-vizek (water/s), tér-terek (square/s), szél-szelek (wind/s), tehén-tehenek (cow/s), etc. Most retain it unchanged: só-sók (salt/s), ház-házak (house/s), szél-szélek (edge/s), méh-méhek (bee/s), etc. Some will lenghten their last stem vowel: kutya-kutyák (dog/s), macska-macskák (cat/s), bika-bikák (bull/s)... And, finally, some may even change their last stem vowel: borjú-borjak/borjúk (calf/calves) [the first alternative is the traditional, the second is a newer form], hó-havak (snow/s), tó-tavak (lake/s),... I think, the best approach is to learn them all by heart.