Thank you for your replies.
I found 330nF capacitor, that's the best I have... When I insert it, bounces are still there (but works as it should be - it sometimes switches the LEDs). In a few days I'll get 100nF, as you suggest, and try it.
I study computer science and I have really have a lot of programming there but noone will teach us how to create even simple circuits or explain how the basic elements work. I just try to do it on my own because it is what I'm interested in. I can sit and try to write a program whenever I want because I was taught how to do it but I can't sit and just build a circut like that. I wanna simply change it :).
I attach another picture of what I did (I know this is not actual schematic, sorry for that). If everything but the value of capacitor is good, I'll just get 100nF as soon as I can and try it.
@polymorph
I'm sorry, I forgot to answer your question. I use the internal pull-up resistor, which, following the datasheet, is 20k.
I attached the photo to my post and changed quote tags to code tags, thanks for that.
