How to prevent apps and processes from launching in background and slowing my device I recently installed GravityBox on my S3 mini. In one setting, I could change the physical button actions, so I decided that a Double Tap on Back would close the current app. It works fine. But it doesn't close it like when I do it manually - that is to say remove from recent apps - it just forces close so when I'm closing that way some apps like Geometry Dash or doesn't save my progress.

Actually it does more than that. I think it stops the most recently launched process since when I'm in some app and sometime I double tap back and it closes another app. And the big problem is that those apps slow drastically my phone. They prevent an action from being executed, they slow the navigation, they make games lag... They are named Google Play Services, Play Store, android.process.media, Messenger... 

And oddly, when everything becomes slow and laggy, all I have to do is to double tap multiple time back button, and when every other app or process is closed everything is fast. But I often close the real current app by doing so. And when I'm in the launcher, I can tap a thousand times back, and there will always be a process called PageBuddyNotySvc the wouldn't close. Or it's LogProvider.
Naming Gavity box running on your device implicates it is rooted, so you could use the full powers of Greenify. Greenify "temporarily freezes" apps which are running in background (of course only those the user specified). Other than with "deactivating" or "freezing" apps using e.g. Titanium Backup, such apps stay available in all places (including the app-drawer) and, in most cases, even can receive notifications (GCM etc.). It's more "putting them to sleep" than "freezing them".

Greenify can be used on non-rooted devices as well, but its full powers are unleashed with root (and the donation package plus the corresponding Xposed-module). Definitely worth a look.