Bubanj ima veliku brzinu centrifugiranja.

Because they are in the accusative singular.

The verb imati (to have) normally takes a direct object, and here the direct object is veliku brzinu centrifugiranja.

• nominative: velika brzina
• accusative: veliku brzinu

The adjective has to agree with the noun, so both change together:

• velika → veliku
• brzina → brzinu

Because after brzina (speed), Croatian often uses the genitive to mean speed of ...

So:

• centrifugiranje = spinning / spin-drying
• centrifugiranja = of spinning / of spin-drying

This is the same pattern as in phrases like:

• brzina kretanja = speed of movement
• brzina vožnje = speed of driving

So brzina centrifugiranja literally means the speed of spinning.

No. Here it is a noun, not a finite verb.

The dictionary form is centrifugiranje, a verbal noun meaning something like spinning or spin-drying. In this sentence it appears in the genitive singular: centrifugiranja.

So even though it comes from a verb idea, in this sentence it behaves grammatically like a noun.

Literally, bubanj means drum. In this context, it means the drum of a washing machine.

So this is not a musical drum here, even though the same word can mean that too. The context makes it clear that it is an appliance part.

Grammatically, bubanj is the subject of the sentence, so it is in the nominative singular.

Because adjective choices do not always match word-for-word between languages.

In Croatian, velika brzina is a normal way to say high speed or great speed. So velik/velika/veliko often covers meanings that English might express with high, great, or large, depending on the noun.

So this is natural Croatian, even if the most literal English equivalent would not be big speed.

Because Croatian has no articles like the or a/an.

English says:

• the drum
• a drum

Croatian just says:

• bubanj

Whether it means the drum, a drum, or just drum depends on the context.

That is very normal in Croatian, and learners usually have to get used to relying on context instead of articles.

Yes, Croatian word order is more flexible than English word order.

The sentence as given:

Bubanj ima veliku brzinu centrifugiranja.

is the most neutral, straightforward order:

• subject
• verb
• object

Other word orders are possible, but they would usually add emphasis or sound more marked. For a learner, the given order is the safest and most natural default.

A useful thing to know is that nj in Croatian is a single sound, like ny in canyon.

So bubanj is approximately:

boo-bany

Also, Croatian spelling is fairly regular:

• j is pronounced like English y
• c is pronounced like ts

So a word like centrifugiranja has a j sound like y, and the nj part near the end is again like ny.