Glad to hear you made it past that. I did a google search for " app\src\main\java\com\epicgames\unreal\GameActivity.java:193: error: cannot find symbol "
and came across this thread.
Two important things is to have the right SDK downloaded in Android Studio and for the SDKConfig in your project settings to point to the right things. (This usually works by default, but sometimes needs to be manually pointed to the correct location)
Also to take a step back to the beginning, this is the first doc you should follow when setting things up.