Generally- "der" is used for referring to male nouns, "die" for female and "das" for neutral ones. There are different rules when the sentence changes a bit (for example, you'll say "das Mädchen" for singular but "die Mädchen" for plural and it gets quite confusing (at least to me) along the way, but you'll learn it in future lessons. Which you may have already gotten to since your comment is 4 months old ;)
How did you know that the comment is old as their no date is mentioned
For example, we can say der Junge, die frau, but " die Jungen/frauen". And das Wasser
I accidentally typed "The beds ar dirty" just because I forgot the E in Are, doesn't mean I don't understand what is being presented and shouldn't be counted against me.
doesn't mean I don't understand what is being presented and shouldn't be counted against me.
Duo is pretty stupid; it can just match answers against a list of translations it has been told are correct. It doesn't actually understand English or German.
Perhaps you may be happier with a human teacher.