If you can access the Play Store, download it officially. If you use an APK, you will likely lose the ability to log into your MyTrainz account, meaning you cannot download community-made content.
If you only download the APK, the game will crash on launch. Place the OBB folder in: Android/obb/com.n3vgames.trainzdriver2/ Trainz Driver 2 Download Apk
Trainz Driver 2 introduced several major upgrades over the original title: If you can access the Play Store, download it officially
