The syatax of the sentence i put in is proper in english or is it because you don't have varied answers yet in the database?
Could be either of those. Without knowing what you wrote, it's impossible to say.
What is the entire sentence that you wrote as an answer?
That should have a comma after "Mara", but Duolingo generally ignores punctuation.
That sentence is rejected because it unnecessarily changes the word order relative to the Klingon sentence.
We expect bIyaj'a', mara? to translate to "Did you understand, Mara?" and mara, bIyaj'a'? to translate to "Mara, did you understand?" -- that is, a vocative (indicating the name of the person you are speaking to) should be translated in the same position in the sentence as in the original.
Sometimes the word order has to be changed for grammatical reasons (to accommodate the different grammar of the two languages or the preferred style), but sometimes, multiple word order are equally possible, and in that case, the original word order should generally be followed -- this is the case with vocatives.