Why is there an apostrophe on "menu's", does it occur after 'u's or something?
No, for the possessive you just add an s unless it causes the same vowel issue.
...and an apostrophe is also added by itself after a word ending in 's' which is like in English, yet after a consonant other than 's' the Dutch possessive has no apostrophe unlike English.
It is irregular, like kind -> kinderen, so it doesn't follow the typical rules.
it's not pronounced correctly by Duolingo, the e in menu should be a schwa
Thank you for this link. The pronunciation has been driving me bananas! Could not understand how "menu" was so similar to English but once pluralized sounded more like "mean-aus."