I send mail and the guy that sells it answer me:
"Hello...I checked out the car's steering, and it seems to turn fully left and right. I am not sure what it means by semi-proportional right and left steering. To me, it can only be turned right or left, what other choises can there be. If you know what it means, I would be interested to know what it means."
So i keep my current car and will program it for bang-bang with LN298. bridge
I asked on modeling-car for car with propotional steering and told me the min value is 90euros... So i keep my 6euro car