You'd normally be able to do something like this with a number of tools. apktool
and dex2jar
are good, jadx
is a great all in one solution too. In this case, it looks like MockingBot uses Cordova to generate your app, meaning there is almost no real Java/Android code to decompile. It is essentially a web wrapper so you can build cross platform apps.
jadx
will still allow you to extract everything from the application, but it might not be easy to reconstruct. I would suggest checking out Apache Cordova, or another project that implements it, such as Ionic if you intend on going this route. If you do, I also suggest using an IDE better for web developing. You can still use Android Studio, but vanilla Intellij might make your life a little easier.
Assuming MockingBot didn't use any Cordova plugins, you can simply unzip the APK and use what falls under the assets/www
directory to start customizing your app using Cordova.
Edit: Because I can't comment without at least 50 points... This actually isn't a duplicate as was already suggested. The question might seem similar, but web wrapped applications are very different from those built using Java and much easier to decompile/reverse. The answer linked in your comments will very likely not help you.