as a pronoun, 'everything' refers to all things or the entirety of a group or category of things. It encompasses the total amount, quantity, or extent of items in question.
Everything is ready for the party.
I've packed everything for our trip.
She told him everything about her day.
'everything' is singular, so it should be paired with singular verbs 'Everything is (not are) going well.' It's often used for emphasis to indicate the totality of items or situations in question.