Klingon sentences are arranged in the order object–verb–subject.
English sentences are usually subject–verb–object.
That means that the subject (the one who does the action) is after the verb in Klingon, while the object (the one who receives or suffers the action) is before the verb.
So sentences may seem backwards.
But beware! You cannot simply start reading from the end; it's only the object and the subject that come in different places in Klingon compared to English.
For example, "Duras and Worf" are DuraS wo'rIv je, with "Duras" and "Worf" coming in the same order in Klingon as in English -- there's no subject/object relationship here.
This different word order is something so basic that it's mentioned in the grammar tips and notes for the very first lesson unit ( https://www.duolingo.com/skill/kl/Useful-phrases/tips-and-notes ) -- so I fear that you are not aware of those tips and notes.
They are not available in mobile apps so far, so you will have to go to the Duolingo website to access them: https://www.duolingo.com/
Then, click on a unit and then on the lightbulb:
(You may instead see a button labelled "tips"; if so, click on that instead.)
I highly recommend doing each lesson unit on the website first, not in an app, though an app can be helpful for repetition and strengthening later.