General Android volume control - how to do it?

Question

Android

Hello! There are Meizu POP wireless headphones
On android 8, the headphones had their own volume level, and the phone had its own. This irritated me terribly. Then, as it turned out, after updating to nine, the sound level became general ... but from the android there was only one volume control - the call, the notification level, the alarm clock were hidden in the settings. It was terribly inconvenient, so I rolled back to 8, where you press the volume button, and three sliders appear, instead of one. but that's not the point.
How to make the overall sound level of the bluetooth headset and phone?