Which language should I learn next?

So I tried to learn Greek because all those funny scribbles look mysterious, I constantly brag about how I can read them. But recently it turned out there is a country where 10 MILLION people know it almost as good as I do.

I want to be the first. The pathfinder. Any language out here that nobody else knows? How would one shock the natives with it?

I've been recently appointed as an advanced japanese teacher (I finished my fourth unit in Duolingo last year, and I plan on finishing my fifth this year). I have been told not to give any translations whatsoever. But I find rather difficult to explain the concept of 日本語上手 because of it is used in various contexts and many translations it has. So I would love if anyone can give me any tips on how to handle this, because I have to do it on the very first class.

Long story but the bird captured me several months ago and has been holding me hostage for not shocking natives enough. I'm trying to bust out by literally busting out my polyglot skills but I'm stuck as for which language to shock with. African is off the table because nobody would take thag seriously... Any help??

Here's a demo: https://youtu.be/hLBpbiwgdOY?feature=shared