The present perfect is formed with the verb have and a past participle. It is another way of expressing the past.

Many verbs have irregular past participles.

be		been	did		done
go		gone	speak		spoken
come		come	give		given
run		run	drink		drunk
fly		flown	eat		eaten
see		seen	show		shown
know		known	forgot		forgotten
begin		begun	write		written
wear		worn	fall		fallen
take		taken	wake		waken
break		broken	awake		awaken
got		gotten

When have is used in the present progressive, it can be contracted with the preceding pronoun.

The present progressive is negated with not. When not is present, have can be contracted with not but it can't be contracted with the preceding pronoun.

To ask a question, have is brought to the front of the sentence.