Still is a verb in that sentence.
Still is an adjective in that example.
Still is an adverb in that sentence.
In a sentence, the word "action" can function as a noun.
it depends what word it is it could be any part of speech depending on the sentence
"When" is an adverb when it begins a sentence.
All subjects are part of speech for they are all nouns.
you
a sentence is a part of speech
Pronoun
Noun
Why is the beginning of a interrogative sentence.
Him is a pronoun.