Learn Croatian: Danas žele pet. - They want five today.

In Croatian, you often drop the subject pronoun because the verb ending already tells you who is doing the action. The verb žele specifically means "they want". If you wanted to emphasize who wants it, you could add oni (they) and say: Danas oni žele pet.

Does the number pet change if they wanted five of a specific feminine or neuter object?

No! Unlike the numbers 1 through 4, which change their endings to match the gender of the noun they count, the numbers 5 and up (like pet) are indeclinable. They are "frozen" and always stay exactly the same, no matter what you are counting.

Why is danas at the beginning of the sentence? Can I say Žele pet danas?

Yes, you can absolutely say Žele pet danas. Croatian word order is very flexible. Putting danas (today) at the front simply puts a little extra emphasis on the time. It is exactly like the difference between saying "Today, they want five" and "They want five today."

What is the dictionary form of žele?

The base form (infinitive) is željeti (to want). The -e ending in žele is the standard present tense ending for "they" for this group of verbs.