Hello there, I want to make plugin to kwin which enables effect like this: http://forum.noxworld.ru/ in your system, where should I start? First learn Qt and OpenGL from scratch?
Is it adequate way to make that effect? Should I look into another way of creating that (like, make a simple application in Python)? I want to make it work as fast as possible.

You need to look at X cursors for that, rather than a KWin plugin.

Using the right tools you probably could extract the cursor the browser creates (although it may not have the sparkles that follow the cursor - that will probably be Javascript so may need to be done using a KWin plugin)

For writing a KWin plugin, you are probably best to ask the KWin developers on their mailing list - kwin@kde.org