AndNav2 does not provide full 'offline navigation', but you can prepare routes i.e. via WiFi. To do so, connect your Android-Device via WiFi (WLAN) and request any route. In the dialog before the route gets visible do not forget to check "Make offline available"! Now when you can see the map open the menu and select the "Preload" menu-item, while having zoomed relatively close to the map. AndNav2 will now ask you to preload several maptiles. Having downloaded these maptiles, you will be able to navigate 'offline' on that route with all maptiles below.