Looking for help decompiling an APK file?

There's not enough information there to go on. Opening files with Notepad isn't usually useful, because any bytes that are not in the current character set will show up as little squares. A hex editor would be more useful. The first few characters could be compared to known "magic numbers." If nothing useful is found that way, there may still be some strings in the file that can tell you what created or encrypted it.

https://en.wikipedia.org/wiki/List_of_file_signatu...

.dat is a very generic file extension, so assuming just the .jpg part is bogus, it still wouldn't tell you anything. .ogg is an audio codec/container, so trying to play it in VLC or importing it into Audacity might yield something useful.

You could also try running the file through a file type checker, such as this one:

https://mark0.net/onlinetrid.html

They can identify more complex and rare file types, and don't rely on file extensions.

apk is probably encrypted to prevent what you are trying to do.

APK is generally just a zip file which can be extracted into the component files with something like 7-zip but it may also be encrypted preventing this.

they are either fakes or encrypted. you need to know what size they are to be sure.