Controling the Car - First Light after a long Tunnel

Today I finally did what I didn't want to do, I dropped the matrix stuff and went to the simpler way to control where the car is by using the combination of position and relative angle. That can be set together to form the matrix I need to position the car-object.

And after trying forever to get something working, this solution indeed does work. The car moves as intended, top speed is too slow and the turn radius is also too small, though. So now I hope I can finally find out, where I went wrong with the matrix code I created before as I can now compare the two matrices when they start to develop in different directions. Then I can look into where I limited top speed and limit the turn radius to sensible values.