Hei Xavier Kahvila ei ole hyvä. The subject is ''kahvila'' and it is a concrete word, an object or a thing. The word ''hyvä'' on the other hand is a predictive, which tells you what the thing is or isn't. (the Café is not good) Remember, the predictive is always in the nominative case when the subject is a concrete word. Tämä kahvi ei ole hyvää. This time the subject ''kahvi" is a meterial word, an abstract word, hence the predictive is always in partitive singular. Negative partitive constructions usually involve a verb. E.g. En osta sanakirjaa. Number 0 and above 2 + partitive singular. E.g. Kaksi miestä, nolla astetta, viisi kirjaa...etc..

Hi Xavier (and Kaj)! "Viisi sokeripalaa" reminds me of this little joke circling the Internet a while back. It's about the multiple different meanings for a simple sentence: "Kuusi palaa". Enjoy! :) https://www.puhutaan-suomea.net/kuusi-palaa-9-meanings-in-finnish/