I have an archive of some .unity3d files: http://www.dropbox.com/s/tr14mn4r1k08nk ... s.zip?dl=0, but I can't extract them due to unknown reason.
I want to learn extraction and repacking method for this situation mainly.
But, I will grateful for right direction with attached sources of information in all other cases.
Game named "Ragnarok Mobile" and can be found on Tap Tap, for example.
I spent a lot of time with trying extract these files, but didn't reach success.
At least, two companies already extracted these files, but I don't think, that they want to share their method with someone else.
But right now, after posting, I will try to ask one of them

Their clients for game patching didn't give me any ideas.
Google has a lot of information about thing called "reverse engineering", but I don't know which one will suit this situation better than others.
P.S. I can be wrong, but I think I tried all free utilities for this purpose, so that is why I called files specific.
P.P.S. I can share apk, extracted apk and obb folder if they will be required.