"Torg, did Mara understand the Klingon?"
Translation:torgh, tlhIngan yaj'a' mara?
No; it’s not grammatical at all in standard Klingon.
“Torg, is Mara definitely a Klingon?” would be torgh, tlhIngan ghaHbej'a' mara'e'?
Without the -'a' suffix, it wouldn’t be a yes–no question, so torgh, tlhIngan ghaHbej mara'e'. would be a statement: “Torg, Mara is definitely a Klingon.”
In Morskan dialect, you can omit the -'e' suffix on the subject of a “to be” sentence, but with the regional pronunciation there, the sentence would be more like ghlIngan ghabej mara.
I don’t think that 'oHbej would be appropriate anywhere, since the pronoun 'oH “it” is not used for beings capable of using language. If you used it deliberately, it would probably be rather insulting.
The word order can be a bit complicated for longer and more complex sentences. But for the simplest and most basic sentences the subject and the object switch places when compared with English. The object (the person or thing the action is done to) goes before the verb and the subject (the person or thing doing the action) goes after the noun. Thus "Mara understands the Klingon" becomes tlhIngan yaj mara.
It is annoying that Duolingo has not included the Tips & Notes in the apps and has even hidden them on web access. None the less, it is possible to access those Tips & Notes even from your mobile device.
To access the Tips & Notes, you will have to access the course using a web browser at https://www.duolingo.com/. You can still do it on your mobile device, but you will have to use the web browser instead of the app. When you click on a Skill, it will expand to reveal a Start button, a key, and a light bulb.
If you click on the light bulb it will reveal the Tips & Notes and give you a detailed explanation of the grammar that is introduced in that Skill. If you have questions after reading the Tips & Notes for any Skills, then please return to the forum to ask your question, explaining what you didn’t understand or what seems contradictory to you.