"Paris is a crowded French city."
Translation:باريس مَدينة فَرَنْسِيّة مُزْدَحِمة.
Paris: subject, the thing we want to talk about. Hence it is first here.
(a) city: here, we are telling the nature of Paris. In other words, if I say باريس مدينة this would translate to (Paris is a city) and NOT (Paris city) or (the city of paris).
The last 2 words are adjectives describing "city" مدينة to complete the meaning. And since مدينة (city) is feminine, these two adjectives come in feminine form.
In Arabic Adjectives come after the noun not Before so You Say in English Blue Pen , while in Arabic u would say " Pen blue