1998 Fuel Pump or Sending Unit Problem?

[checo16]

So I've been having this problem for about a year now & I still haven't found the solution to it. If you guys had this type of problem & solved it, can you please tell me what was wrong and how you fixed it.

It doesn't matter how much I fill the tank up to, but after cruising around whatever I have left of fuel it'll only be displayed when the key is on. And when the ignition switch is off it'll stay on to whatever I filled it up to. (In other words, the fuel needle doesn't go down like it's suppose to when the ignition is off.

Here's the video I uploaded to show you what my car does: