So, today I got ordered switches from WASDKeyboards, and OK, everything is OK, and then I called my friend which is a proffesional in electronics.
And then, we opened the keyboard with a card and screwdriver, removed the board (just pull it out, it isn't soldered to anything), and then we started.
When he saw the board, he automatically said, that that board is a Chinese shit (:D, what would you think that a pro would say), but, I said him that my number "4" isn't working anymore, and after a 5 seconds he said that the soldering is really bad made with bad copper and that it might not work because of it, firstly I wasn't sure, but then he took a voltmeter, and connected it to the pins, I pressed the key (switch) and it was working just fine

He desoldered the switch, and yes, we put a new switch, just for case, but the old switch was working as I stated, OK!

So ye, if anyone of you got into this, and suspects in a switch, firstly look at the soldering, and try the switch with voltmeter

As I said before, I'm not the best at electronics, and this might sound to someone pretty ussual/everyday stuff, but to me it was something new, that I must say, very enjoyed

Also, here are the pics, from the video I took, which I might upload if there will be any interest, here
http://imgur.com/a/zfSab#0
Thank you all for helping me to decide what to do!
