Window on top, active without focus

[El Don]

Hi, I'm writing a program that acts as a notification, but I want the window to be active without stealing focus, for example, if I press del, it closes no matter what I'm doing in the computer, also i want it to be on top of everything, even games, is that possible?

I'm a beginner, and found something about an API called ShowWindowPos but I don't really understand it.

Thanks in advance