Learn Croatian: Njemački auto je brz. - The German car is fast.

Normally, yes! Most Croatian nouns ending in '-o' (like selo or meso) are neuter. However, auto is short for automobil, which is masculine. It keeps its masculine gender even in the short form, which is why the adjectives njemački and brz take their masculine forms here.

Why does njemački end in '-i' while brz has no special ending, since they both describe the same car?

In Croatian, masculine adjectives have definite (ending in '-i') and indefinite (no ending) forms. Adjectives for nationalities, like njemački, always take the definite '-i' ending. The word brz is indefinite here because it is being used after the verb to state a new fact about the car.

Could I change the word order and say Njemački je auto brz?

Yes, you can! The verb je is an enclitic, which means it is a weak word that must sit in the second position of a sentence. The first position can be counted as a single word (Njemački) or as a whole connected phrase (Njemački auto), so both word orders are perfectly correct.