Hello radnaj and Ilja Maljutenko Thanks for your inputs on this subject.
Not all cars are equal. A utilitary car would have absolutly no problem going up or down this road. However, a SUV or a Crossover car is another story.
This road has been tagged in a way that represents what's the reality here.
The highway now has the tags:
incline=up
lanes=1
narrow=yes
This should do it.
Please note that Openstreetmap is a database and not a data consumption client like a navigation app and in the end a navigation app decides how to interpret osm data.