What benefit would there be for Kim Jong-Un, and how would DPRK soldiers communicate in Arabic or Russian?
Money.
They are essentially mercs. They fight, and Kim Jong-un gets the money. The Pyongyang regime is a slave lord. They dispatch workers all around the world. The regime pockets most of the money which is supposed to be paid to the workers, who gets a tiny amount of their official paycheck.
“how would DPRK soldiers communicate in Arabic or Russian?”
They wouldn’t. Regular soldiers just take orders - they only need a commander who can speak another language