thanks for your answer NikLaw. I did what you wrote but its the same.
I can see the slider, it is ( doing nothing ) on 50 % at the beginning.
If i push the brake pedal, the slider goes from 50 % up to 100 % and
if i push the speed pedal, it goes from 50 % down to 0.
So if i press the speed pedal it brakes and speed up the same time.
In all the other games i tested i had no problem at all with that SL 6698.