No notification sounds on the Razer phone 2 when connected to bluetooth in Android 9.0 Pie

When I connect my Razer Phone 2 (Android 9.0) to a Bluetooth headset, all the notifications sound will go to the head set. And it's not possible to change this, so the phone itself make a sound notification.
As long as I have the headset in my ear, it's no problem, because then I can hear the sound notification (SMS, email etc). But if I'm at work I don't want to have the headset in my ear all day. At least i don't. I use it when i get or make a call.I now miss SMS or email, because I don't get any notification. I know it's possible to turn on vibration, but at work I don't always get notified because the phone is not in my pocket.
I search hard to find a solution, but I just find other with the same problem, and it's stars with Android 9.It's possible to go to the Bluetooth device and turn off the media sound, but then it don't work if I want to listen to music.
There should bee a way to switch where you want your notification, or possibility to turn it on at your phone and your Bluetooth device at the same time.