I can confirm too: I studied this at the university like this and also in Hebrew it works the same way. Quite problematic how it can mix us, people who have a different mother tongue than Arabic or Hebrew, but we can get used to it and actually it makes sense, even if it's really hard not to mix up the exact meaning of a sentence or an expression. Practice, practice, practice! :) With Duo and with original sources! :)
@Jasper - actually there's as much difference between "The pretty door" and "The door is pretty" in Arabic as there is in English. To describe a noun, the adjective has to have the same gender, number, and definiteness as the noun. In the given sentence the noun is definite but the adjective is indefinite. Hence the given Arabic sentence can only mean "The door is pretty".