Learn German: Die Leistung war so gut, dass sie den Rekord gebrochen hat. - The performance was so good that she broke the record.

This sentence uses so and dass to link a cause to its result. The adjective gut (good) sits directly after so in the main clause, and the result is explained in the subordinate clause starting with dass. A comma always separates the main clause from the dass clause.

Does sie in this sentence mean "she" or "it"?

Based on the English translation provided, sie means "she" (referring to a female person). However, because Leistung is a feminine noun, sie could grammatically also refer back to the performance, meaning "it". In a real conversation, the surrounding context would make it clear which one is meant.

Why is the verb hat at the very end instead of right after sie?

The word dass is a subordinating conjunction, which means it forces the conjugated verb to the very end of its clause. Since this clause uses the conversational past tense, the conjugated helping verb hat lands at the end, right after the past participle gebrochen.

Why is it den Rekord and not der Rekord?