"I am eating pasta."
Translation:Ich esse Nudeln.
In English the default tense for expressing action verbs is the present progressive. It is formed by using the verb to be as the conjugated helping verb and the present participle of the main verb. I am eating, I am working, I am swimming, etc. Most languages don't use their progressive tense as often as English, but some languages like German and French don't even have a progressive tense. In German the present tense is the only way to translate a couple if different English constructions. It is the same with the auxiliary verb do that is used in questions, negation, and occasionally in statements. Ich esse is not only the correct translation for I eat, but also for I am eating and I do eat. If you add a translation of the auxiliary verbs a German speaker who didn't speak English would have no idea what it means.
It's a matter of conjugation. In the present indicative Essen is conjugated
So isst is the he/she/it conjugation and esst is the plural familiar you conjugation. Whenever you see different forms of what you know to be the same verb, it will always be related to the conjugation and/or the tense or mood.
ALL German plurals use die. Die is used for all feminine nouns in the singular, but all masculine, feminine or neuter plurals. It has its own position essentially in case tables. That's why there are no feminine nouns that are the same in the singular as the plural, although there are some masculine and neuter ones that are.
You have to distinguish between incorrect and not accepted on Duo. Each exercise has its own unique database of accepted answers, and I doubt many of them contain all the conceivable solutions. If you find one that isn't included, you can report it. New exercises will generally have more possibilities forgotten since Duo will accept correct reported options, although it take time. But this exercise is seven years old. The fact that there's no discussion about Teigwaren tells me that even the native and advanced speakers didn't "miss" it. I think Teigwaren is somewhat more of a technical classification term. I never heard it used colloquially when I lived in Germany, although I am more persuaded by the seven year history of this exercise. But feel free to report it if you want.
Well, Essen is an irregular verb, so it has to be learned somewhat individually. But English verbs are different from those of many European languages in that they don't have many different conjugations. Regular English verbs only are different in the third person singular for regular verbs. But although conjugation for German is probably easier than for a romance language, you will still have some different forms to learn. Glancing at the conjugation is one of the first things most people do when learning a new verb, although Duo's method doesn't generally have people reciting conjugations like I did in High school French. As a general rule, ich forms end in e, du forms end in st, er/sie/usted end in t and the wir and sie/Sie forms are like the infinitive. But there are several patterns, including what I would call patterned irregular verbs. But it's why a quick glance at the conjugation will help you notice how any verb varies from the norm.