Klingon uses the prefixes as a conjugation system to show who is doing the action, but also who the action is done to. In other words, the prefixes tell you the grammatical subject AND the grammatical object. The jI- prefix tells us the the person speaking is doing the action, but it is not being done to any particular object. So jIyaj means, "I understand". The vI- prefix also means that "I" am doing the action, but in addition indicates that there is an object and it is third person (not "you" or "me"). So, vIyaj means, "I understand it/him/her/them." (In conversation, context will usually clarify whether you should translate it as it, him, her, or them. Duolingo does not usually provide any context so it accepts each of those four answers.)
Similarly, bI- means, "you (singular) - no object", ju- means, "you (singular) - us", and cho- means, "you (singular) - me". Though Duolingo has not made the Tips available on the app, there are grammar explanations available for you. If you have not been reading the Tips, I would like to ask that you review those.
If you are doing the course on iOS or Android, you cannot currently access the Tips through the app. To access the Tips, 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 (or a small light bulb button - the small light bulb button is pictured here).
If you click on the Tips button it will reveal the Tips and give you a detailed explanation of the grammar that is introduced in that Skill.
If you have questions after reading the Tips for any Skills, we are happy to answer your questions, but many of your questions will probably already be answered in the Tips.
In this listening exercise I have to write in Klingon what I hear. I can't hear a difference between the gh and the H. They all sound equal to me in this exercise. In other exercises I can hear a difference. Is the recording quality in this exercise not ideal or is this a usual pronounciation and do I have to get used to it?
I feel the difference between the two sounds although it took me a while because those are sounds we are not used to in our native languages. A neurological conditioning is needed to perceive spoken sounds we are not used to and the differences between 2 sounds we are not used to discriminate and to produce. The older you are, more difficoult it could be. So you just have to listen to it many times and maybe good quality headphones could help. Hope you'll get it soon pal! Qapla' bathl je!