Learn German: Ich muss morgen aufs Amt gehen. - I have to go to the office tomorrow.

In German, a Büro is a regular workplace or business office. An Amt specifically refers to a government or public administration office, like a registry office, immigration office, or tax office.

Why do we use aufs here instead of zum for "to the"?

For certain public institutions and authorities like an Amt (government office) or Bank (bank), German traditionally uses the preposition auf to express going there. This gives us auf das Amt, which naturally contracts to aufs Amt.

Why is it aufs (auf das) and not auf dem?

auf is a two-way preposition. Because you are actively moving towards a destination in this sentence (gehen), it takes the accusative case (das Amt). If you were already there and not moving, you would use the dative case to show a fixed location: Ich bin auf dem Amt (I am at the government office).

Why does morgen come before aufs Amt?

German sentences generally follow the "Time before Place" rule. The time element (morgen, meaning tomorrow) naturally comes before the place or destination element (aufs Amt, meaning to the office).