It takes a long time to start/load the app. And Also when I navigate to pages there is a delay of 2,3 seconds. Overall it is slower than normal android Apps. How do I reduce loading time and speed up the App for Android?
Ionic guys are working hard so the 4.0 version of Ionic gets faster. Just check this tweet from one of the Ionic's core developers to see the performance improvements in 4.0 alpha versions.
I also recommend you to build your .apk in an optimized way. This is the command I use in order to build the .apk for production, which makes the app faster and smaller:
ionic cordova build android --prod --aot --minifyjs --minifycss --optimizejs --release