I want to use my Arduino to make handsfree calls just like my car is doing. When I connect my phone to my car via Bluetooth I can access my contacts or dial a number in my car and a call is made via my phone.
I want to do exactly that with my android. However the only information I find on the internet is how to connect and send serial data via an application on the phone.
The Arduino cannot send audio.
Currently Bluetooth LE does not support audio, because it was designed for low power sensor and accessories. That’s what most new Bluetooth products like the Arduino Nano 33 BLE use.
You will need a Bluetooth Classic module or one that supports both.
Here is one from Silicon Labs. This is not a one-off hobby project product.
Oh, okey. Would it be possible through USB then?
USB has been available for much longer than Bluetooth. You can find a lot of information on how to create USB Arduino projects.
Have a look at the Teensy family. There are a couple of easy USB tutorials including support for audio. I have not tested the USB audio device examples where the Arduino connects as a USB audio device over USB but I have tested USB mouse, keyboard and the audio processing with the Teensy libraries and they were fairly easy to use.
https://www.pjrc.com/teensy/td_libs_Audio.html
Whether USB audio will allow you to do what you want, I do not know. USB is not the easiest thing for beginners.