Learn Italian: Il numero di cantieri non cresce più. - The number of construction sites is no longer growing.

To say "not anymore" or "no longer", Italian uses non before the verb and più immediately after it. Here, they sandwich the verb cresce to make non cresce più (is no longer growing).

Why is the verb cresce singular if there are multiple construction sites (cantieri)?

The subject of the sentence is il numero (the number), which is singular. The phrase di cantieri just describes what the number consists of. Since the verb must agree with il numero, it takes the singular form cresce.

Why is it di cantieri instead of dei cantieri?

We use the simple preposition di (of) without combining it with the definite article "the" (i) because we are talking about construction sites in a general, undefined sense. If we meant a specific, known group of sites, we would use the combined form dei cantieri (of the construction sites).

The English translation says "is no longer growing". Why doesn't the Italian sentence use a continuous tense?

In Italian, the regular present tense (cresce) is frequently used to express actions happening right now. While you could technically use the continuous form here (non sta più crescendo), the simple present is much more common and perfectly translates to the English "-ing" form in this context.