Learn Swedish: Personalen arbetade beslutsamt vid kassan under strömavbrottet. - The staff worked resolutely at the checkout during the power outage.

This sentence is a perfect example of the Swedish Sätt-Rum-Tid (Manner-Place-Time) rule. In the end part of a sentence, Swedish orders these adverbs strictly: first how it happened (beslutsamt), then where (vid kassan), and finally when (under strömavbrottet).

Could I emphasize the time by moving under strömavbrottet to the beginning of the sentence?

Yes, but you must remember the V2 (verb-second) rule. If you start with the time phrase, the verb must come next: Under strömavbrottet arbetade personalen beslutsamt vid kassan. Notice that the manner and place phrases keep their relative order at the end.

Why is the adverb beslutsamt spelled with a -t at the end?

Adverbs of manner (how something is done) are usually formed by adding a -t to the base adjective. The adjective for resolute is beslutsam, so the adverb becomes beslutsamt.

Why do we use the preposition vid for 'at the checkout' instead of på?

In Swedish, vid means 'by' or 'next to' a specific point. When someone is working at a checkout counter, desk, or machine, they are standing next to it. Using på would imply the staff were physically standing on top of the cash registers!