Ghost experiences, do you believe in them?

A few years ago I saw a “smokey” like figure that looked like an older woman wearing a nightgown. I couldn’t make out her face. And when I was younger, I use to feel someone brushing by me, tapping me on the shoulder, or making things move or lights go out round me. I use to say “stop it grandpa” and it quit. I don’t have nmy memories of grandpa, he died when I as18 months old but I believe he does (did) that to me. I’ve been told that what I described is something grandpa would have done when he was alive because he was a pranktser. Has anyone else experenced anything else like this? Do you believe passed on loved ones come back to protect you or mess with you?