I agree that this looks scammy. Normally I would also try to contact them. Preferably by phone or even visiting their address. But a visit is most of the time impossible. Cause I wouldn't travel hours and spend a few hundred of dollars.
About arbitrage possibilities, I have seen a few of those based on CMC data. Sometimes the data was incorrect at CMC. And most of the time I didn't know how to benefit as I could not register an account in Korea. Or once your money is in Korea or such a country I can't get it back into the Netherlands. At least not with my private bank account.
You can transfer back your money from Korea through crypto...
That's right, but it does mean a risk. Especially when you only earned like 10% profit on the first trade. That whole profit could disappear again. I'm actually quite certain you can't benefit from arbitrage by trading with only $50 or similar small amounts.