To ask someone if they had fun, I could say:
Hast du Spaß gehabt?
But why is it
gehabt, and not
gehaben? How is the participle formed?
Would I still ask it formally using
Haben Sie Spaß gehabt?
I thought the participle might have been conjugated like the verb is, i.e. 'gehaben' with 'Sie' and 'gehast' with 'Du', but maybe not?