"Is he reading?"
I do not get this... and really do not understand the explanation above
Please go on helping, SaintDayz. We need to be here for each other through this. If someone is trying to help and makes a mistake, hopefully someone else will point it out. A little temporary confusion is a small price to pay.
On the subject of questions, it's in yes/no questions that the verb comes first. You can ask a question with an interrogative word followed by the verb, e.g. "Wo ist der Mann?"
I believe that the verb lesen in german already means 'to be reading' or 'to read'. So 'er liest' means 'he reads' and 'he is reading'. Adding 'ist' would make it 'is he is reading'. Someone with much better grasp of languages will be able to explain with all the applicable grammatical terminology about tenses.
So I‘m a native and I’ve come to inform you! There is in fact another way to say someone is doing something. You can say they’re „am“ and then the infinitive of the verb. So for example: „Er ist am lesen.“ that actually means „he is reading.“ yet; this is usually used as an explaination for why someone can’t do something else. So if someone asks for help you can say „Ich bin am lesen“ to use it as an excuse for not helping them. It is also sometimes used casually in other kinds of situations but I think it’s less common than just saying „ich lese“. Yet; I’m quite disappointed Duo doesn’t accept the „am“-Version...
Questions are generally formed with verb - subject inversion. German does not have as many verb aspect as English so there is no word-for-word translation of Is he reading?, but:
The typical non-question form of that is He is reading. To form a standard question, we move the to be verb so that it precedes the noun. This happens in German too, just slightly differently due to variations in grammar rules.
He is reading translates to Er liest. In simple sentences like this, it's actually simpler to form a German question. Just put the verb in front of the noun. Liest er?
On the other hand, you can say He reads in English, but to form a question, you can't just switch the words. Reads he? doesn't make sense. We have to add a word. Does he read? So don't panic, it's simple.
Because in some languages such as German and French the verb and the subject are transposed to form a question. You can say (I believe, and I am no expert but having been trying to learn languages for yrs) Er liest? and Liest er? and they both mean Is he reading?/He reads? Intonation is also a factor, just as in English, when asking a question the tone rises at the end of the phrase/sentence.
It would help learners of English who must find using "do" in questions difficult. That said, we do invert subject and verb in English to ask questions but in a limited way, e.g. "May I?" "Would you?" "Can he?" "Will she?"
Isn't it strange how we absorb syntax as babies yet don't know the grammatical rules. What is the rule here? I don't know and I'm a native speaker. Is it a rule about modal verbs and about the future tense?
Ist er liest
That's grammatical nonsense in German. A bit like "Does he is reading?" -- you added a helping verb that does not belong in the sentence.
German does not need a helping verb "to be" to form the present tense. Liest er? is quite enough to ask "Is he reading?".