Is there out a real task killer?

I was lookng for a real task killer. Some experiences which realy working???
I tryed some, but if i go into apps push the apps they “killed” han still i can use the button for “force shut down” (hope it’s the right translation from german). So for me they dont work or i understud something wrong ^^

Hi ralph ,
I use Greenify. It’s more of an automatic task hibernator, but it keep resources and battery available for me. If I want to kill tasks, I use the system option.

You Don’t Need to Install a Task Manager: How to Manage Running Apps on Android

Why RAM Boosters And Task Killers Are Bad For Your Android

Otherwise Greenify