Translation:The Klingon does not understand Federation Standard.
I see a report from the same time as your comment (possibly from you?) that "The Klingon does not understood English" should be accepted.
The problem in that sentence is not "English"; the problem is the verb "does not understood".
(I'm guessing this was a multiple-choice exercise? Where the system picked one of the correct answers, "The Klingon does not understand English", and replaced the word "understand" with "understood" to create a distractor sentence.)
How do you understand the order of the sentence?
Klingon word order is basically OVS: object–verb–subject.
Here, the verb is yajbe' "does not understand" -- or a bit more precisely, "he does not understand it". (The absence of a verb prefix indicates that the subject is one of "he, she, it, they" and there is either no object or the object is one of "him, her, it, them".*)
What's after the verb is the subject: the person who acts. In this case, tlhIngan "the Klingon". (This refers to a person, not to a language. The Klingon language is tlhIngan Hol, where Hol means "language" -- tlhIngan Hol is thus more literally "the Klingons' language" or "the language of the Klingons".)
And what's before the verb is the object: the thing which gets acted upon. In this case, DIvI' Hol "Federation Standard". (Literally, "the Federation's language" or "the language of the Federation", from DIvI' "federation, association" and Hol "language".)
So the person who acts is tlhIngan "the Klingon"; what he does is yajbe' "doesn't understand"; and the thing which he or she doesn't understand is DIvI' Hol.
Thus we have "The Klingon does not understand Federation Standard" as the translation into English.
Note that in English, the subject comes before the verb and the object comes after it -- the opposite of the Klingon word order. So in order to get a natural-sounding English sentence, you have to rearrange the words.
* But it can't mean "They do not understand it."; the combination of "subject = they, object = him/her/it" would require the verb prefix lu-. This will get taught later.
Since Klingon is so different from English, it can be difficult and confusing to try to figure out what is going on. Have you read the Tips? The Tips have a lot of grammar information that can help explain what you are seeing. Duolingo has hidden the Tips, so I want to make sure you know about them and where to find them. If you have not been reading the Tips, I think you will find them very helpful.
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