Lots of similar questions on here, i know as i asked a few of them similar to this, there is always good info from this forum.
I hardly ever use Apple car play now as its just a pain.
The only thing im aware of with the apple car play is that you cannot use both Apple cp and Audi phone but you can still use maps etc.
The way i switch is by pressing phone icon on side of screen, then following the prompts i.e connect to MMI.
The other thing i have done is to turn off the wifi connection between phone and car as this stops internet connection (i trialled the free data pack and used it up quite quickly, so dont think its a viable option going forward, i only streamed music, this also seemed to be the only way to get Amazon alexa to play music too)
the only funtion this seems to loose is the calender app??
to listen to music from phone press and hold the speech button and then request song, album etc. ignore the prompts they dissapear
I also programmed the steering wheel button * to change from radio to music as requesting music doesnt switch to music.
Its really simple once you get your head around it but poor functionality from Audi
Good luck with and im sure there are different ways of doing the same, so do update and let us know what you found