People who are saved are escorted by two angels into Abraham's mansion in another dimension.  It happened to grandpa Campbell and it happened to me so I was allowed to see what happens.

Before Christ, the devil held the keys to the gate to the underworld "death and the grave".  Generally and as far as I know the only spirits were nature spirits, angels and shadow entities created by demons who roamed the earth among the living at that time.  This is the part many religious unenlightened believe still exists.

When Christ broke the gates to the underworld he took his people with him back to Abraham's mansion.  Many others who could not be held in that realm departed as there was nothing to stop them.

There are angels who's task it is to round them up and take them to a waiting place until they can be sorted out.  I've been to a few of these places in spirit and they look similar to a huge school house.  The souls are placed in what looks like a gymnasium.  They are taken in sets again by two angels, these look like humans.  There are portals in these buildings that look like elevators.  Some go up and some go down.  When a soul is sorted it will either go up or down in one of those portals.

I've seen people who have been taken by an angel literally go screaming and kicking for one reason or another.  Some of them do not even know they are dead.  To them it is like a living nightmare, its all real to them.  It's like they literally went to sleep and woke in a never ending nightmare filled with creatures and strange things that do not fit into their former understanding of reality.

Others who were bound by demons could not leave and so remained in the Underworld.  There is no hope for them.

Shadow entities created by demons within human beings frequently do take on human form and yes they do their best to trick people into thinking they are the ghost of someone dead.  This is why Jesus spoke of the gift of discernment.

The demon Nata took on a human form when he came here to try to convince me not to close the portal here.  I knew he was a demon and not a ghost.  We fought and though he left thinking himself to be the winner of that fight he was the one who left laughing manically.

One night while OBE I was throwing the shadow entities out of the house, a never ending job until the portal was closed and house was sanctified against them.  I threw some out and was watching the ghost gathered in the street as they could see all these things.  They were curious.  More ghosts gathered each night to watch me.  These were not demons, or shadow entities they were ghosts of souls who once were alive but died.

I was looking toward them in the street when Nata flew over and I followed him also flying.  When I caught him I asked him in the name of Jesus tell me his name and he hit me and said "who wants to know?"  Then he ran.  He did not recognize me.

I caught him again and demanded in the name of Jesus tell me his name and he said Nata.  Hit me and dove into his portal. I dove in after him catching him the third time I demanded him tell me his name and he said "My name is Nata but you can call me Charlie Wheeler."  When I looked up there were demons in their demon form all around me, many of them 8-12 feet tall.  Needless to say I left in a hurry.

So yes I've seen demons in human form and demon form.

Nata told me the name of the man who's form he was using at the time.  Charlie Wheeler.

The spirit of cancer can speak and if the spirit of cancer can speak like a human then what else might pretend to be human?

Jesus spoke to spirits.  Bound shadow entities and unclean spirits and cast them out.

At that time before his death as far as I know there were no ghosts, as they were held in the Underworld until he broke the gates to that world.  There was no reason for him to speak of ghosts of the dead.

When he died on the cross the veil in the temple between the Holy of Holies and the front chamber was ripped in half.  This meaning the spirit of God was now among the living giving us access to the place where only the priests were allow previously.

There was a great earthquake.  Walls cracked and some fell.

The dead were observed walking among the living that day as if they had returned from the dead.  This will happen again when the Lord returns.

Certainly some of us have seen things that human eyes can not see without God's help.  His purpose in showing some of us these things is so we can explain and answer questions that were not answered for us in the Bible or by our religious leaders.

I do not recommend anyone investigating the paranormal or UFOs without gaining some education from someone who knows the dangers.

As for your friend who said there are no ghosts, they should stay away from such things as it is clear they are not enlightened.  It is not a field for someone to "dabble" in for the very reason they said.  Demons can and will take the form of humans.  So do angels.  And both of them do it to fool the living.  God himself has appeared in human form.  The angels who Enoch was with in heaven he refereed to as men and called them by their names.

A witch once told me there is no such thing as demons or God or angels, only elementals.  That woman is bound by demons.  Her unwillingness to accept and face the truth has allowed the demons to bind not only her but most of her family.

After death there are demons who do their best to control certain ghosts.  There are serious bad things that go on in the spirit world.

If you can get Ghost Adventures there watch the episodes of The Mackey Music Hall - "Hell's Gate."  Be sure Zack knows demons haunt places.  And there are both ghosts and demons in that place.
Quite a few people still insist there are no such things as ghosts.  Some who don't believe in God, or the devil insist there is no life after death.  There have been a few skeptics who have died and returned to tell their stories of things they saw while on the other side, now complete believers in the spirit world.

Others are religious minded people who like to believe they are "in the know" and "well informed" when the truth is they are not enlightened.  They live in a concept world created for them by someone else who was also unenlightened.

I've had highly religious people tell me things like "God doesn't speak to people anymore."  In direct conflict with the Bible saying that in that day God will dwell in the hearts and minds of His people.  In direct conflict with the fact that when Christ died on the cross the earth shook and the veil between the sanctuary and the holy of Holies was ripped in half.  The dead were seen walking about on earth again as if they had returned from the dead. 
The lost books of the bible tell what happened when Christ descended into the underworld to get his people.

Some believe the bible is the Living Word of God and exclude everything else.  What they fail to accept is that Jesus had, read from and taught from texts that are not printed in the bible.  If they were good enough for Jesus they are good enough for anyone.

So those among us who are more enlightened must ask, why do some people who believe in God understand these things while others do not?
In some cases the people simply refuse to accept the truth.  They choose to be blind when it comes to spiritual things.  Some think the Bible tells the entire story, when in fact it's just a tiny slice somewhere near the middle.  Some think the bible is the Living Word of God, but I can tell you from experience the Living Word of God is alive and yes can and does speak with His children.

Below is a message from me to someone who asked about these things as they have a friend who tells them there's no such thing as ghosts.  They have another friend who tells them there's no life after death also. :-)  While being in spirit form after death is not exactly living it's still a form of existing.