The reason it is done with rar was because the game got too large for the apk so it was split in order to still have it on android. You just need to move the archive.rpa file to the game folder of lucky.paradox.
I’m not sure why your android won’t download rar files. Is it something on your settings or maybe a recent android update? But to extract the files you just need the rar app or the Zarchiver app that will let you do that.