Learn Dutch: Als de docent de fout niet ontdekt, hebben we vijftien minuten pauze. - If the teacher does not discover the mistake, we have a fifteen-minute break.

In a subordinate clause (a clause starting with words like als), the verb is pushed to the very end of the sentence. The negative word niet usually goes right before that final verb. If this were a regular main clause, it would be De docent ontdekt de fout niet, but the als moves ontdekt to the end, leaving it right after niet.

Why does the second half of the sentence say hebben we instead of we hebben?

This happens because of the Dutch verb-second rule. The entire first part of the sentence (Als de docent de fout niet ontdekt) counts as position number one. To keep the main verb in the second position, hebben must come right after the comma, pushing the subject (we) behind it.

Why doesn't the Dutch sentence use the word een (a) for 'a fifteen-minute break'?

In Dutch, you can state a duration directly before the activity without an article, literally saying 'fifteen minutes break' (vijftien minuten pauze). If you wanted to use een, you would have to word it differently, like een pauze van vijftien minuten (a break of fifteen minutes).

Could als also mean 'when' here?

Yes, als means both 'if' and 'when' in Dutch. You have to rely on context to tell them apart. Here, 'if' makes the most sense because the teacher finding the mistake is a condition or possibility, not a guaranteed future event.