Yes, getting to know all of them. Unfurtunatelly, words in German do not have the same gender as they do in English, or in Portuguese (my native language). It is also strange for me to say "Der Apfel" (gender masculine), if in Portuguese we say "a maçã (the apple)" that is feminine.
Anyway, you will have to see each word's gender and remember that.
Basically: you have to learn the gender when you learn the word.
I suggest that you learn words not individually, e.g. "newspaper = Zeitung", but together with their gender, e.g. "the newspaper = die Zeitung" so that you will know what it what.
With some nouns, you can recognise the gender by the ending (e.g. pretty much all nouns with the ending -ung are feminine), but often, you cannot guess and simply have to learn it.
Is there some trick to knowing which form of "to read" I should be using?
It's none of those -- it's die Zeitung with capital Z (since it's a noun).
die, because the word Zeitung is grammatically feminine (like most words with the ending -ung).
Grammatical gender is not, in general, logical, so you can't ask "why" -- it's just something you have to learn together with the word.
Not always accepted. I got "am reading" wrong SEVERAL times. It's why I'm asking. The answer "context" makes no sense. I'm intelligent enough to check for that, and always do, but still get it marked wrong anyway.
Lots of folks put their faith in this app only to have it marked wrong by idiots.
I got "am reading" wrong SEVERAL times.
I'm intelligent enough to check for that, and always do, but still get it marked wrong anyway.
I can't see what you see, so I can't comment on what was marked right or wrong for you.
A screenshot of such answers marked wrong where you can't understand why would be really helpful here.
only to have it marked wrong by idiots.
Yup. A computer is pretty much an idiot. It's a very fast idiot, but still an idiot.
And how would a screenshot help me here? There are no ways to add an attachment.
You would have to upload it to a website and paste the URL into a comment.
If you're a mod, then someone hired you.
I receive no money for my work on Duolingo and do this in my spare time.
As do all the forum moderators and course contributors, as far as I know.
They obviously aren't acting on the flagged reports.
I think you severely underestimate how many flagged reports there are and severely overestimate how much free time the volunteer course contributors have.
I think there are more hundreds of thousands reports. On a really good day, I can go through maybe 300. So if I worked through reports every single day, I'd take years to get through them all. But I don't have time for Duolingo every day, nor do I have time for 300 reports every day.
There are two or three other "active" contributors but I don't think they visit the site every day, either.
It takes a while. Years, sometimes.
How do we know it's die Zeitung and not Der or Das? Why das Buch? And same for other words, just how do we know?
You look it up in the dictionary and memorise it.
Sometimes, you can tell from the ending (e.g. most words ending in -ung, including Zeitung, are feminine), but mostly, you can't.
Sometimes, the same word can even have multiple genders depending on its meaning, e.g. der Leiter = the leader / die Leiter = the ladder.
Ich habe einen Apfel. means "I have an apple."
Ich habe den Apfel. means "I have the apple."
In both cases, Apfel is in the accusative case -- but in the first sentence, it's indefinite (an apple -- not any particular one) and in the second sentence, it's definite (the apple -- a particular apple that the listener can identify, perhaps because you've talked about it before or because there is only one apple present).
Finally, apfel with a small a is not a German word. Capitalisation is part of the correct spelling in German; please do not ignore it.
Why is newspaper feminine?
It isn't. English nouns such as "newspaper" do not have a grammatical gender.
The German word Zeitung is feminine. But remember that noun gender in German is mostly arbitrary, so there's rarely a reason why a particular noun has a particular gender. It's usually simply something to look up and memorise.