Subwoofer not working and low rear speakers volume

[ionmarandici]

Hello. I recently purchased a 2014 A4 B8.5 2.0TDI Multitronic. It has the Audi Sound System with the subwoofer on the rear shelf. The subwoofer doesn’t seem to be working, and the rear speakers volume is considerably lower than the front speakers. I’m new to Audi and thought maybe I am missing out on something. I also scanned the car for fault codes and there are none. Anybody know how I might go about figuring this out? Thanks