Bluetooth rc crawler chasis

Hey guys,
I might have started a project which is a little bit over my knowledge and I´m wondering if you can support me on that. (Hints, walkthrough, links, etc. I appreciate everything)

The idea:
I have a crawler chasis (see picture) and want to make it move via an app created with MIT App Inventor and a Raspberry Pi 3b+.

In detail:
Electricity is set up and working. I tested all the outputs from the Raspberry, The chains are moving as intended when I type down the programm in the Raspberry console. The next step would be to connect the app (which I later want to have on my phone) with the Raspberry and enable bluetooth communication and control the chains via app

The Problem:
I have absolutely no idea how a bluetooth connection is set up and if my idea is even possible (I highly think so but not 100% sure)

What I would like to achieve: If bluetooth connection is enabled and the phone/app connects to the raspberry I would like to control the movement like an RC Car. Currently it is only the chains which need to be controlled, later it will be more.

Any idea? Thanks in advance.