Do wicked people have knowledge in the afterlife?

yes, they know why they are there in hell

Why did Jesus speak of death as a sleep?

Because a sleeping person is inactive. During deep sleep there is no consciousness of surroundings or the passing of time. There is no pain or suffering.

Similarly, in death there is no activity or activity or consciousness. But the comparison goes further with sleep.

With sleep, one expects to wake up. And that is exactly the hope that the Bible offers for the dead.

This would be the resurrection that Jesus spoke about.

Jesus’ early disciples clearly understood the true condition of the dead. To the followers of Jesus death was a sleep, and the grave a resting-place.

God knows what happens to us when we die, and he has told us that when a person dies, his life ends. Death is the opposite of life.

 So when someone dies, his feelings and memories do not keep on living somewhere else.  When we die we can’t see, we can’t hear, and we can’t think anymore.

Yes, they'll know why they're being purified of their sins.

All people will give an account of what they did in this life to God.

So a person will have knowledge of what they did in this life in-order to give the account of their actions to God.

Romans 14:12 “So then every one of us shall give account of himself to God.”

Only profoundly superstitious and gullible folks are experts on the afterlife..

Until judgement day when they will be tossed into the lack of fire and meet their second death...

Everybody has knowledge in the afterlife.  And all sinners are wicked, you included. The Lord Jesus Christ is God, and He loves you.  Believing in the Lord Jesus Christ means being forgiven all sins past and future, and means going to heaven and not hell.  Death leads to immediate heaven or hell, and it is too late to be saved, after death.  All believers still sin.  See 1 John 1:8.  To be in heaven and not hell, believe in the Lord Jesus Christ, who is God and who died on the cross and shed His blood to pay for all of our sins in full, and who was buried, and who resurrected from the dead.  The only way to avoid hell is by believing in the Lord Jesus Christ, without adding any of your own works.  See Romans 4:5, 1 Corinthians 15:3-4, and John 3:16.

THEY WONT BE GOING unless they turn over a new leaf and repent and get saved.

What do you mean "knowledge"? Like a special insight and enlightenment? Then no. No human does. Or if you mean have they heard of the concept of heaven and hell, then yes.