@mariamaria123,
There is nothing whatsoever stopping you from going over to him and talking first.
See how often you have to do that. Is it all the time? And I mean over time, as in, more than a week.
Let's say 10 days go by, and you approach him 10 out of 10 times. Then feel free to ask him, "You're really friendly online, but you never seem to approach me. Why is that? You know we're friends, right?"
And see what happens. While the different language (and culture, BTW) might be an issue, there are also people who are extremely self-conscious about who they hang out with, thinking that it makes some sort of a statement about who they are. This is magnified, big time, in junior high/middle school, and is also magnified (albeit less so) in high school.
Or he's a jerk, embarrassed to be seen with you.
It's your mission to find out (if this matters so much to you) what's going on here.
So open your mouth and ask, instead of hanging around and wondering.