Is it possible to adjust the throttle or brake sensitivity of the PS4 Controller in Race Driver Grid?

I connected my controller to the PC via USB cable and adjusted the key assignment in the game settings. Now it is like this that when pressing the R2 and L2 keys I accelerate / brake only 0% or 100% (when steering with the sticks it works). This causes the tires of the cars to spin and I break out at the latest in the curve. Does one know how to correct this problem? Maybe with a mod?

Turning on the grip assistant in the game options works, but at the expense of driving pleasure.