Various Problems - NO ROOT and Stock ROM

Hi,

My configuration is:
Android Version: 6.0.1 (MMB29V)
Kernel Version: 3.4.0-gbaedb01
NO ROOT - Stock ROM

Problems:

1) Microphone: when I make calls, my voice seems a little electronic and not clear to the other end
AFAIK this problem is there from the beginning (lollipop or JB I don't remember)

2) I cannot use speakerphone because there is a lot of noise (seems I'm in the middle of an hurricane)
AFAIK this problem is there from the beginning (lollipop or JB I don't remember)

3) Sometimes when pressing the on/off button (while locked), it vibrate and the camera app appears.
From this moment the front camera is unavailable and I have to restart the phone to get it working again.
This problem appared after upgrading to Andorid 6.0

I searched the internet and found only some suggestion to disable OK Google (for the mic problem).
I tried it, (also tried to disable google now), the situation is a little better, but my voice is still disturbed.


Hope you can help me...

Rooting and installing a custom rom could possibly resolve the situation?

Thank in advance...

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