The app can create routes and recalculate them only using Internet. It doesn’t support downloading maps for offline use. But you can download a route to drive it offline. To do it, create a route, start it, access menu on the same screen and select “Save route”.
Please note that you need to be logged in to save a route.
To start the saved route, access the side menu, tap on the username to get to the profile screen, and further to Routes section. Select the needed route and start it.