Raspberry Pi 4 between receiver and flight controller

I have TBS Crossfire Micro TX, Nano RX and Raspberry Pi 4, I haven’t bought a flight controller yet because I have a problem:

Until the drone receives a special command from the transmitter - I control the drone in manual mode, but as soon as it is received, the Raspberry algorithm should control the drone.
I don’t know how to implement it, in what order to connect it all, so I’m asking for advice :slight_smile: