Hello, my name is Hyensoo. You can call me John.
I’m a South Korean student developer. I just wanted to contribute to some open source projects, and I found here. It’s my honor to help as much as I can. Especially, translating english to Korean would be brilliant. I want to do some programming part as well, but actually I have no idea how to begin in that part. I would appreciate enormously if somebody show me certain way.
Whatsoever, it’s great to be in! 
-Sincerely, John
I have no clue about translation. But if you want to code something for Mozilla (not necessarily related to MDN) try to hack on debugger.html. It’s super easy to work on, the team is really nice and they have a slack channel. You need basic web dev skills.
If you are more into systems programming, try out contributing to Servo. This might be more complicated but some people prefer to work low level rather than build web stuff.
Contributions to both projects end up in Firefox.
Hi Hyensoo, or John (I will call you whichever you prefer)!
Welcome to our community! We could definitely use more help with translation into Korean. I admit I’m not sure what the state of that content is, although I can say that the list of ongoing “active” contributors is currently empty on the localization project page, located here: https://mzl.la/2vRXxMU
You can find information about localizing MDN here: https://mzl.la/2gYGmq8
You’ll find we’re a helpful bunch of people. I hope you can find things to do and get involved, because there’s always room for more help!
Eric Shepherd
Senior Technical Writer
Mozilla
Welcome Hyensoo!
Nice to have you here. 
I am new to the MDN Project, too.
Currently I help tranlsating the learning area of MDN to German, but hope to be able to help with more code stuff soon, too.
I found you really have to look yourself a bit where you want to contribute, what work needs to be done and what you can do.
But you can find all the information easily, there are lots of guides and when you have questions, you can ask here in the forum or on IRC and get answers quickly.
Don’t be afraid to just start translating. At the beginning I was a bit cautious, too. But you have to see it like a Wikipedia for all webdev stuff, so you can just start making changes without asking for permission. If you really make a mistake, there is a version control system and things can be reverted back quickly.
Just start where you think “This should be done”!