Is there an easy way to change in flight the route. It happens that due to weather or restrictions you need to change your planned course during flight. It is possible by stop navigating, perform the changes and activate navigation again but is there no easier way to do this?

More than one easier way. This is all detailed in the documentation, but in short, you can easily make changes using the What's Here menu, which comes up when you press and hold on the map. You can add waypoints to your route and remove them in this way.