Care to do a bit of thinking for me...?

Before you start screaming how i should do most of the thinking myself, let me tell you that I know it's up to me. :)

I was Black in this one:
http://de.lichess.org/analyse/g0h2clct/black

Even though my oponent silently closed his tab after I castled kingside, I'm fairly new to chess and I'm not sure if it was due to a high chance that I might've won or he simply lost interest after
the first check I gave.
This was the first game I tried to do a bit more thinking than usual.

I'd appreciate it you could give me a few pointers as to what could've been better.
Or, if you're generous and ready to scratch my back and make my ego purr, you could tell me I did a wonderful job and my oponent was just very very bad in what he was doing. :o

:o

I'm pretty sure he knew he couldn't win from there.

Sometimes people just have to suddenly leave (like if there is a zombie alert) or lose the Internet connection (in case of a nuclear explosion) or just close the tab (in case of a boss arriving).
We will never know what happened. You won and that's it.

Indeed, but since his grandma chased him off the computer, he knew for that reason he couldn't win. :D So then Black won.

Hell, his grandma was probably a zombie. Or a nuclear explosion. (Or his boss.) I don't see how people get brought up to play those games. What happened, to the extent of (x) detail, is what we
will never know.

You were in a winning position, which is probably why your opponent left the game. Your opponent was pretty weak... here's a short analysis of the biggest mistakes on both sides:

1. on move 5 you could have killed his rook with your bishop.
2. on move 10 your opponent should not have killed your bishop, since rooks are more valuable than bishops
3. on move 15 your opponent should not have killed your knight, since rooks are more valuable than knights
4. on move 19, you should have taken the bishop with your knight or at least moved your knight- you let him kill your knight for free

I hope that helps a bit- keep on playing!