https://amzn.to/3ynkk4T
Poor Man's AutoPilot w/ BMW Traffic Jam Assist

Things you'll need:
1. An i3 that already has the ability to do self-parking and adaptive cruise control
2. Dongle from https://quidzel.com/
google around for the links as they seem to have moved or hire someone to do this for you.
3. E-Sys software -
4. PSdZDATA (Lite) Files for ESYS: dead links - sorry

Like I mentioned, if you're not comfortable doing this, find a local bmw shop to do this for you

Reminder: TJA won't work unless a number of conditions are satisfied. Car in front of you for the system to track, good lane markings (passing through an intersection will disengage the system) and must be going below the minimum speed for the system.

Good Luck! Have Fun!

Dongle I use: https://amzn.to/2XExAOS