Here, 'about' modifies the numeral adjective 'fifty' (meaning approximately). Words modifying adjectives are adverbs.

'About' indicates movement relative to 'the room' (meaning around or here and there in). It is a preposition.

Here, 'even' describes the action of making something level or equal. It functions as a verb.

Here, 'Even' modifies the entire noun phrase to add emphasis or surprise. It functions as an adverb.

'Even' describes the state or quality of the numbers. Therefore, it functions as an adjective.

Here, 'down' shows the relationship between the movement 'walked' and the object 'the street', functioning as a preposition.

In the phrasal verb 'turn down' (meaning to reject), 'down' functions as a particle, which is grammatically classified as an adverb.

It describes the action of the event occurring. It is the main verb of the clause.

In phrasal verbs, the preposition-like word that changes the verb's meaning (like 'up') is called a particle.

'Regarding' functions as a preposition meaning 'about' or 'concerning'.