Hi,
Newbie flyer.
Is it better to turn of the wifi and bleutooth and 4g/5g (or do not distub button) to use the dji app, when flying, or is this no problem ?

The problem is that the maps are not being shown, unless you download them before.
I never turn it off myself and never had issues, apart from people calling me.
But that can be ignored.

I used to set airplane mode as I dont want to be disturbed by phone calls or notifications.   when a call comes in it overrides the screen leaving you out of the fly app.  

Hi there. Thank you for bringing this query to us. You may run the DJI Fly app without turning on the Bluetooth as this only requires when you perform the QuickTransfer (available in selected aircraft versions) feature on the DJI Fly app. Also turning on Wi-Fi or internet connection is only recommended if you perform a firmware update. Lastly, we highly recommended to turn off Bluetooth on your mobile device to improve signal reception. Hope this helps. Thank you for your valued support.