Technically yes. Round is a synonym (Meaning a word that has the same meaning/definition as another word) of circular. But if that were the case, the phrase would instead be, "Die Orange ist kreisförmig," meaning "The orange is circular." Just a native American-English speaker passing by to help anyone in need of support.
German nouns have different genders. Not sexual, but grammatical genders. Masculine nouns like 'Apfel' use 'der'. Feminine nouns like 'Orange' use 'die'.
Unfortunately no. It's one of those learn the article with the noun kind of things. So instead of learning apple=Apfel, learn apple=der Apfel. There are some websites that group some words together in a gender, but they're only guidelines. Happy learning. Feel free to ask me any questions. I'll help you the best I can, as l am still learning as well.
I think in the beginning lesson it states in the description that Masculine, Feminine, or Neuter nouns don't correspond with the social idea of Gender, which means that an apple in the German language could be a Masculine noun, a cow could be a Feminine noun, and a girl could be a Neuter noun.
Here is a website called Forvo and could be very useful. Just click the blue arrows :) https://forvo.com/word/de/orange/ If you perfer to use the IPA, here is Orange: [oˈʁaŋʒə] oder [oˈʁɑ̃ːʒə] (By the way, don't forget to ALWAYS capitalise nouns in German regardless of where they are in a Word)