Learn Hardcore Polish: Kucharz mówi, że sukces wymaga wielu prób. - The chef says that success requires many attempts.

że is a conjunction meaning that, used to introduce a subordinate clause after verbs of saying, thinking, perceiving, etc. In Kucharz mówi, że…, it links mówi (“he says”) with the content of what is said.

Why is there a comma before że?

In Polish, subordinate clauses introduced by że are normally set off from the main clause with a comma.

What case is sukces in, and what role does it play in the sentence?

sukces is in the nominative singular. It functions as the subject of the subordinate clause (sukces wymaga wielu prób).

What does wymaga mean and which case does it govern?

wymaga means requires or demands. The verb wymagać always takes an object in the genitive case, so whatever is being required must appear in genitive.

Why is it wielu prób and not wiele prób?

The quantifier wiele (many) has an irregular genitive form wielu. Since wymagać demands genitive, both wiele and the noun próba shift into genitive plural: wielu prób.

Does próba only mean “attempt” here, or can it have other meanings?

próba can mean:
• an attempt or trial (as in trying something out)
• a rehearsal (e.g. for music or theater)
Context tells you which sense fits—in this sentence it’s “attempt.”

Can I say dużo prób instead of wielu prób?

Yes. dużo (“a lot of”) also governs the genitive case, so dużo prób is a perfectly natural alternative meaning “many attempts.”

Why isn’t there an article like “a” or “the” before Kucharz?

Polish has no articles. A bare noun like Kucharz can be translated as “a cook” or “the cook” depending on context—in Polish you simply rely on context or add words like pewien (“a certain”) or demonstratives to specify.