Double-clicking on the trash opens a new finder window instead of displaying deleted files when the trash is empty. When I throw a file by dragging it to the trash every thing in the screen disappears except the doc. What can I do?

When you double-click on the Trash icon that has not been emptied, a Finder window will open reflecting the contents of the Trash. You can right-click on any item in the Trash, and from the contextual menu, select Put Back to return the item from the Trash to its original filesystem location. Or, you can command-Drag the item from the Trash to another filesystem location.

Files are not deleted until you purposely empty the Trash.

I am sitting here in front of El Capitan (10.11.1). There is an item in the Trash. Whether I left single-click, or double-click on the Trash icon, or via right-click, and select open, the unemptied Trash will open in a special Finder window whose title is Trash. It will also behave this way after the Trash is emptied — using either mouse action. This is default behavior for El Capitan. I have not customized anything, and I cannot reproduce what you describe.

If you have a file in the Trash that the operating system, or an application continues to access, then it cannot be deleted until it is no longer in use. In the case of the operating system, that would require a reboot, before the file can be emptied from the Trash.