it is very important to know that German language have 4 cases. The Possessive Pronouns are conjugated in accordance to these cases and genders. for instance conjugation of unser (our) for Masculine gender would be like this :
full chart is available at : https://deutsch.lingolia.com/en/grammar/pronouns/possessive-pronouns
which is derived originally from the main definite articles (der/das/die/dem.....) chart: https://upload.wikimedia.org/wikipedia/commons/thumb/5/5c/German_die_der_das_declensions.svg/775px-German_die_der_das_declensions.svg.png
i suggest to memorize the picture of the last chart. it will be useful.
I am no native speaker, but here are my 2 cents:
die Nominativ Form: The nominative case is the "basic" form of nouns and articles. This is the form in which we usually see the subject of a sentence. He likes apples. Er mag Äpfel.
die Akkusativ Form: The accusative case is usually used to describe the object of a sentence, to which something is done etc. He likes him. Er mag ihn I think the majority of verbs in the German language require the subject to be in the accusative case.
die Dativ Form: The dative case is usually used to describe an object in a sentence to which something is given (some verbs also require this case, but they are fewer). He gives the apple to him. Er gibt ihm den Apfel.
Notice how you can see all three cases in the last example. 'Er' is in the "basic" case (Nom.), 'den Apfel' is in the accusative case (masculine nouns change their article, so instead of being der Apfel, it is now den Apfel) (Akk.) and 'ihm' is in the dative case (Dat.)
I am still in the middle of an A1 course here in Germany and we haven't learnt the genitive case so I couldn't tell you much about it.
I am very open to corrections, anyway, hope this helps!
Why are we not using unser ( Possessive ) over here instead of unseren ( Accusative )?
"possessive" and "accusative" are not exclusive.
unser is the masculine nominative, neuter nominative, or neuter accusative form of the possessive determiner "our".
unseren is the masculine accusative form of that possessive determiner.
What is the English translation of this sentence like?
"We need our dog"
English has case only for personal pronouns -- not for determiners such as "the, a, this, our".
Thank you! Now I can see it. Thank you for your patience.
I can see that it was a listening exercise -- the instructions are "type what you hear".
So you should have heard Der Hund frisst mein Buch.
But you did not write Der Hund frisst mein Buch.
Instead, you wrote, the dog is eating my book
Thus your answer is wrong -- you didn't type what you heard.
Duolingo then tells you:
Der Hund frisst mein Buch!
which you can see is different from what you typed.
I do have a screenshot for this
Excellent! Those are always helpful.
where do I send it please?
Upload it to a website somewhere, please -- for example, an image-sharing website such as imgur or Flickr. Or Google Drive or Dropbox or something. As long as you can get a URL that's visible to / shared with anyone, any website is fine.
Then post the URL of the image in a comment here, please.
Thank you very much!
My answer was correct but was marked wrong!
Then I'll bet you 50 lingots that your answer was wrong.
If you can have a screenshot showing the question that you had and the answer that you gave, please upload it to a website somewhere (e.g. imgur) and post the URL of the image here.
If Duolingo made a mistake in rejecting your answer, I will give you 50 lingots and see whether I can fix the problem.
If you were correctly marked wrong, I will explain the error.
In the future, though, please only post statements such as "was marked wrong" if you can provide evidence of an answer being rejected. Or at least quote your entire answer and say what kind of exercise you had (translation, listening, fill in the blank, multiple choice, ...).