I saw the same things, OP.

Demon faces flying toward me. I wasn't afraid and was able to just watch them appear and fade away.

Now I see what I call "real" people and sometimes they speak to me or acknowledge my presence.

I also listen in on conversations between them and most of the time I don't understand what they're talking about.

I saw a woman, once, looking out a window. She turned and looked directly at me and said "This is where it happened".

I asked what happened, but she faded away.
I've had other experiences like this and every time I try to communicate they disappear.

They speak to me, but won't answer when I speak to them.