The -'a' suffix turns a statement into a question. val torgh. "Torg is smart." -- val'a' torgh? "Is Torg smart?"
This is explained in the Tips & Notes. If you have not been reading the Tips & Notes, I would like to ask that you review those so we don’t have to continuously repeat the information that we have explained there. If you have read them and still have a question, please be specific in your question so we can figure out where the confusion is.
If you are doing the course on iOS or Android, you probably cannot currently access the Tips & Notes through the app (though they do plan to add that feature in the near future). 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 (or you can do it from a computer). When you click on a Skill, it will expand to reveal a Start button and a Tips button.
If you click on the Tips button 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, then please return to the forum to ask your question, explaining what you didn’t understand or what seems contradictory to you.
Is the question mark required? Is val'a' torgh accepable?
On Duolingo, most punctuation is ignored. So you can write val'a' torgh with or without a question mark.
When we just write Klingon, most people use punctuation the way they would in English -- with question marks ? after questions, periods . after statements, etc.