frequent phone call interruptions, Samsung GT-I9192, 4.4.2 (S4 min dual sim)

Hi,
I am sadly no mobile expert and need your kind support. Since over half a year I have 2 problems

• very frequent phone call interruptions


• much lower battery life time

My phone/sim provider in Germany are Vodafone and Congstar. But I do not think its related to them.

All the trouble started after a certain upgrade to newer versions of Android OS, but can't remember when this exactly started. Then the battery life went down significantly and I get those annoying interruptions in phone calls up to 3-4 times in a ~15 minute call. Its so bad .. What could you recommend to me ?
Is there a better image downloadable, maybe fallback to older version ?
Or is it possible to fallback to the version in ROM ? I fear side effects and unfixed system holes by this.
Thanks for any help !
BR

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Unable to root LG G2 D802 4.4.2. 3.4.0

Hi All,

I am trying to root my LG G2 D802 (KitKat 4.4.2, Kernel 3.4.0) by using IOroot. I am getting the error:

Mounting system RW and pushing SU, then remounting system RO again
mount: Operation not permitted
failed to copy 'su' to '/system/xbin/su': Read-only file system
Unable to open /system/xbin/su: No such file or directory
Unable to open /system/xbin/su: No such file or directory
mount: Operation not permitted
Installing superuser
4371 KB/s (1468798 bytes in 0.328s)
pkg: /data/local/tmp/superuser.apk
Success

In addition I checked and the phone seems to be rooted (with a couple of apps).

1. Why am I getting these errors?
2. I tried to install twrp and it seems its installed, however I am not able to backup, I am getting a message its cannot mount system, data, etc..

Any ideas? Thanks

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