How do i make forum on App?
You are well know in java programming & XML, then create a apps, it's easy for you, Android application have lot of resources at internet, you must be huge practice at Android studio.
Yes, using Java and Android Studio. You can find courses for both online.
if you are looking to know online courses please look here: https://kiranverma45.blogspot.com/2022/04/how-to-become-successful-java-developer.html