Navigation system calculates totally wrong

Hello I have a new Murano (EZ 12/2006) and have found that the navigation system does not calculate the route correctly. I checked the settings and in my opinion everything should be right (fastest route, incl. highway etc.). Nevertheless, the navigation system usually wants to send me to the shortest route, which is not the fastest. Only after some time, if I drive my route (not those that the navigation system suggests) changes or calculates. avisystem new and see here, the travel time is much shorter. Usually the navigation system penetrant wants to bring me back to its route. So I should turn around and make a detour. Absolutely meaningless. I can stand right in front of a motorway driveway and nevertheless the Navi does not want to get me over the highway to the destination. If then I drive on the highway then it wants to take me away again at the next exit. Does any of you have a solution or someone has d he same problems? Can someone tell me which is the latest, latest version of the navigation system? How do I find out which version is installed on me? I think the software should be quite up-to-date. At least the Junction Views (realistic picture of intersections) are displayed. Thank you for your help. jojoluz