Android-System causes my smartphone to lag The Process Àndroid-System causes my Smartphone to lag very often since it uses much CPU and drains my battery.
Restart does not work.
There is no other process using as much CPU.

MediaServer seems not to be the problem.

Phone: LG G2 "LG-D802"

Android 4.4.2

Kernel 3.4.0

How can I fix this problem?
What you're seeing is probably not Android System itself, but rather MediaServer, which in case you download a corrupted file might cause problems.

I would recommend trying to delete whatever you downloaded in the past few days, and in case that doesn't work, perform a factory reset.