"The bags are not outside."
Translation:Nincsenek kint a táskák.
Then you should continue the sentence with a phrase like: "hanem bent".
Nincsenek sounds better on it's own.
If you say that something is (or isn't) somewhere, you need a form of van. In this case the form of van is nincsenek.
Thank you :-) Does it mean, that the word "van" is ALWAYS a part of nincs/nincsenek? Maybe I didn't understand something essential at the very beginning.
Yes. Nincs is basically the lovechild of nem and van. Whenever nem van or nem vannak would appear in a sentence, you replace them with nincs or nincsenek instead, respectively. Those are basically (very weird) conjugation forms of van.
It also works with sem + van/vannak, resulting in sincs and sincsenek.
Itt sincs túró. - Hier gibt es auch keinen Quark. Sehr platzsparend. :D