Hello guys.
I'm new to the forum and since I can't figure out what this problem is I said to myself it might be worth the shot to try here as well.

Basically I own the car for a year and a half let's say and for like 6 month I've had problems with the sound system in the car.
Let me explain
It first started with the sound completely not working and coming back to life in few minutes.
Then from minutes it progressively jumped to hours, days , months.
What happens is that when I turn the volume **** it says Volume currently unavailable.
If I go to radio I can select the station but no sound whatsoever
If I go to media whatever media source I select it would just get stuck on Loading medium or device
and If I go to tone to adjust the sound, first of all the subwoofer section dissappeard completely and no other option I can modify. It's stuck to a fixed position.

Now the thing is that I checked everything that I could think of. I tried everything I found online. I tried resetting the mmi, tried unplugging the power of the unit and plugging it back on. Checked the fuses , check the cables as much as I could but I still can't figure out the problem.

I was wondering if anyone experienced that before and had a fix for it.
oh and BTW my sound system is the standard one and I'm dealing with an MMI 3g high plus or smtg.
Does anyone have a diagram on how all the MMI units and cables are spread across the vehicle ?
any help is much appreciated.
Thank you guys !

Also I have put a Carista tester on the car and the errors I get are : Radio, Optical Databus and Connection of the Digital Sound Package to the Radio