Learn Swedish: Barnen uppförde sig bra på museet. - The children behaved well at the museum.

The verb att uppföra sig (to behave) is reflexive in Swedish, meaning it requires a pronoun that points back to the subject. Without sig, the verb att uppföra means to perform a play or construct a building. Since the subject here is barnen (they), the correct reflexive pronoun is sig.

Is bra an adjective or an adverb here? Why not use väl?

It acts as an adverb describing how the children behaved. While väl is the traditional adverb for 'well', bra is commonly used as both an adjective and an adverb in everyday Swedish. Saying uppförde sig väl is also perfectly correct but sounds a bit more formal.

Why is the definite form museet and not 'museumet'?

Swedish nouns of Latin origin that end in -um, such as ett museum or ett centrum, drop the -um ending before attaching the definite suffix -et. Therefore, it correctly becomes museet.

Why use the preposition på for the museum instead of i?