Here is the Better Steering Mod for Farming Simulator 2015.
Version: v 1.8

Although I have a steering wheel, but almost always play with the keyboard. On winding roads, I am again and again landed in the ditch in front of nights or power poles.
Now I have invented this script. It varies depending on the speed, the steering speed, the return speed (autoRotateBackSpeed) and the maximum steering angle. It also turns the camera to match the Lenkeinschlag.Beide functions can also be off again.

Controls:
- ksmCAMERA [Shift Left + C]: Moving Camera on / off, default is on
- ksmENABLE [Shift Left + E]: Adaptive steering on / off, default is on
- ksmREVERSE [Shift Left + R]: Look backwards on / off, default is on
- ksmPLUS [Ctrl + E Links]: increase sensitivity
- ksmMINUS [Ctrl + C Links]: lower sensitivity
- ksmUP, ksmDOWN, ksmLEFT, ksmRIGHT [Shift Right + Cursor]: look forward, backwards, left right

Credits:
Mogli aka biedens