Here is how the carplay works, you need to forget/remove your car's BT from the phone. You plug in the carplay to the car, join that bluetooth, the device converts your phone to wifi connection and that is how carplay is pushed. You won't be able to use wifi on your phone if you are wirelessly connected to the carplay2air device.
If anyone is a programmer, knows C, this may be of interest. Looks like a company in China leaked the apple carplay code and it is what is used in that carplay2air dongle
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What I am hoping to see in the future, is someone to take the above code/source and get this working on a raspberry pi zero w. This would allow us to make our own dongles for cheap.