How to lower global media volume of Doogee X30? Even on lowest media volume (slider on first non-silent stop) the output is way too loud. I am trying to lower a value of a media slider's starting point (ideally  decrease volume of at least first half of volume levels of slider).

In engineering mode I tried changing values to lower, but it doesn't seem to be doing anything. After every change I clicked the set button. I have even tried restarting the phone, but the result is same. Even on lowest slider value the volume is very loud (like at 3/4 of my previous phone's maximal volume). I was changing values in Hardware Testing -&gt; Audio -&gt; Normal mode -&gt; Type = Media.

Am I even changing the right values? Because even if I set some level to 0, or even maximal volume to 0, sound volume doesn't change at all.

Edit:
Oh, didn't know Doogee is not a known manufacturer (in our country it's being sold commonly in shops along Apple, Google and Samsung products).

It's a newly purchased phone (week old), nothing custom like ROM, root, xposed or anything like that (don't even know what xposed is). I have installed a bunch of apps, but I don't think that they can change such settings in vanilla Android.

Device name: Doogee X30
Android: 7.0
Go to Settings -> Sound, and then scroll to the bottom, where you'll find a feature called Sound enhancement

Try and toggle the volume booster button on/off.