So for Android app development, you can go one of three ways:
Each has its own pros and cons. If you're new to Android app development in general, the easiest way for you to get started would be to use
Android Studio. and Java, which is the baked beans of Android development, and powers most of the apps on Android. Flutter and Kotlin are emerging, promising technologies, but are not good if this is your first time around.
ALSO last but not least, you always have the (imo best) option of turning your website into a PWA. You'll be able to keep the stack you like (I'm assuming, since it's an MMO, HTML/CSS/JS/Node or Typescript backend) and access native functionalities and API's. This is very often overlooked, when oftentimes a PWA is all you really need, especially since to distribute a PWA you don't need to go through the App Store or Google Play, both of which are proprietary and charge fees.