Learn Finnish: Kaupunki uudistaa vanhan kaluston nopeasti. - The city renews the old fleet quickly.

This ending marks a total object, meaning the action is complete and encompasses the whole group. The city is renewing the entire old fleet. If the sentence used the partitive (vanhaa kalustoa), it would imply an ongoing process or that only a part of the fleet is being renewed.

How does the verb uudistaa relate to the word for 'new'?

It is built directly from the adjective uusi (new). By adding the verb-forming suffix -staa or -istaa to the consonant stem uud-, it creates a transitive verb that literally means 'to make new' or 'to renew.'

The word kalusto translates to 'fleet' here. How does it differ from the similar-looking word kaluste?

Kalusto is a collective noun referring to a full set of equipment, rolling stock, or a fleet of vehicles, like a city's buses. Kaluste refers to a single piece of furniture or a fixture, and is most often used in the plural kalusteet meaning furniture.

Why is the adverb nopeasti placed at the very end of the sentence?

In Finnish, the default, neutral position for an adverb of manner (describing how something is done) is at the end of the clause. You could say Kaupunki uudistaa nopeasti vanhan kaluston, but placing it at the end sounds the most natural for a standard statement.