mwhy is my nexus 7 either not responding or freezing or taking forever to open a app . i rooted it it still didnt work than i unrooted it using the tool kit both times still doesnt work . what would could the proble
Rooting just (if it's done right) just adds a file named su to a folder named /system/xbin. It does nothing to apps that don't need root (like all the apps that came with the phone).
Have you tried Safe Mode? If that works, one of your installed apps is misbehaving.
If not, have you tried clearing cache in Settings in Storage?
If not, have you backed everything up, done a factory reset, then restored things one at a time?
There are a lot of reasons the phone could be acting that way - you have to eliminate them one at a time.