Ever since then we have celebrated the day by gaily lighting up our homes with lamps.

I have to under line adverbs in the given senetnce.

adverb ="ever", "since","then"

In "lighting up" ,Is "up" an adverb?

I would consider 'then' a noun meaning 'that time', 'since' a preposition meaning 'from' and 'ever' and intensifier of the prepositional phrase, the whole acting as an adverbial.

'Up' is an adverb: 'gaily lighting our homes up'.