Chaos Vehicle (for a small car)

Hello, I used the video tutorial to get the car running, but since my car is much smaller in size (like a toy car), the physics are completely messed up. I can’t figure it out myself anyway, could someone help me to get the car to behave as it should?

I would somehow send my file and someone would make the changes and send it back to me.

I’m ready to even pay a little for it, since no one cares about doing it for free anyway.