No question that modals can be tough, but very useful in conversation. An interesting thing to remember is the relative strength of statements in regards to whether the statement is positive or negative. Zum Beispiel (for example) Dürfen positive is a soft statement. Darf ich jetzt spielen? (May I play now?) Soft. Dürfen negative is strong. Du darfst nicht rauchen. (You are not allowed to smoke.) Strong. Müssen positive is strong. Wir müssen unsere Tiere füttern. (We have to feed our animals.) Strong. Müssen negative is soft. Sie muss nicht schwimmen. (She does not have to swim.) Soft.
Philip, not being a native speaker, please take my opinion with that understanding. However, I often use "solte," meaning "really should." I've noticed that the other modals, such as "muss," "konnen" drop into their past tense to indicate "gotta" or "really." By the time they drop into their subjunctive, the voice is strained a bit more to indicate that. I belong to a conversational group, and that's all they do is talk, most of them more fluent than I. For "sollen" try out "Ich soll gehen," vs. "Ich sollte gehen," vs. "Ich sollte gegangen sein." The difference is slight, but in English we'd say softly, "I should go;" with a little more force, "I really should go;" and being a little upset, "I should have gone." Where "nicht" fits in I feel that it simply negates the sentence with the same amount of verbal force as the other sentences.
Are you sure about this? As a beginner non-native German speaker it seems there are three different possibilities to describe the situation, if not the sentence: müssen nicht= must not (eg because it's poisoned) dürfen nicht = not allowed to (eg because you have to wait for others) ????? = do not have to eat (because it's your personal choice)
But maybe I've got the wrong sense of müssen, probably because it sounds so like must in English
I am not a native German speaker but Dutch, but the system is Dutch is roughlu the same as in German. So, müssen = must and dürfen = may (also can in contemporary English).
So far, so good, but the problem is with the "not". In English the not belongs to the following part: You must not eat = you must (not eat). So there is an obligation to not eat. Same with may.
In German and Dutch the not belongs to the modal verb. Sie müssen es nicht essen = Sie (müssen nicht) es essen. I.e. There is not an obligation (müssen nicht) to eat. Or in other words it is the negative of Sie müssen es essen. The latter is an obligation to eat so the former is not an obligation to eat or they are allowed not to eat. In English expressed by may: They may (not eat it).
In the same way: Sie dürfen es nicht essen = negation of (Sie dürfen es essen) = they are not allowed to eat it. In English: they must (not eat it).
I thought it sounded like "Sie mussen Essen nicht essen." when played at normal speed. I had to slow it down to hear that she was saying "Es". As for your comment, it is common for doctors to say that you must not eat food before a medical procedure. That is how I understood it, anyway.
Krys, you are perfectly correct, IMO. I'd say "Sie solten es nicht essen" to soften it a bit, meaning "should not eat it," whereas I'd say "Sie müsten es nicht essen!" to place more emphasis, as "really not at all" eat it. Duo is a language class, not mathematics, so often there is not one correct "solution." Have a Lingot.
What is negated by /not/? German: the modal verb; English: the action verb.
English: "You are allowed to refuse it..."
German:"You are not allowed to eat it.".
English: "You are required to refuse it.:"
German:""You are not required to eat it.
Note: You meant Sie (you) instead of sie (she or they).
There is an enormous response to this use of "müssen." I think it is because we jumble up "must," "may," and "should" in English. Throw in "might" just for more confusion. Try not to get hung up on this unless you are a language teacher or linguist. I must...or should?...or "oughta?" get going...now. Go with Duo for this and move on to something else. You must/should/might/could do yourself a favor.
negation of modal verbs works differently in English and German. The positive "you must"/"du musst" defines a definite obligation. But whereas in German the negation "du musst nicht" only states the lack of such an obligation (= "you don't have to"), which is better translated as "you need not", in English the negation "you must not" defines that there is an obligation not to do it, which in German is expressed as "du darfst nicht".
"They haven't to eat it"? That makes no sense. "Haven't" is short for "have not" (e.g., "They haven't / have not eaten it"); it doesn't normally work in the same circumstances as "do not have."
"Haven't" and "do not have" are hardly ever interchangeable. "I haven't any [noun]" is possible but not a usual phrasing; otherwise they're definitely not interchangeable.