Can someone tell me
1. does GNUEmacs see diference between different programming languages or it has just some built in keywords

2. Can I change syntax highlihting of buffer which isn't saved or has another .extension (for example change to c++ highlight in file which is already open and has .sql extension or has no extension at all)

3. if GNUEmacs has font locking for different languages How can I add new font locking scheme(for example if I want font locking for .prg files(foxpro/clipper))

As I understood I can add new keywords to GNUEmacs I will look through that in documentation.

Any help is appreciated

First of all, "GNU" and "Emacs" are separate words.

For 1. and 2., you want to look at the section Major Modes in the Emacs manual.

Thanks, looked through your link, 1. and 2. points are clear

To solve third people should use M-x load-library and then load some lisp library foo.el, or even easier just set (load "foo.el") in emacs initialization file

---------------------------------------------------------------

Problem is just that I can't find any library for foxpro or clipper font locking(syntax highlighting), so it would be cool, if someone would throw some link!

A quick google came up with xbase mode, but it doesn't appear to have been updated recently. Still, you might want to try it.

Thanks for xbase, it is better than nothing! But works quite laggy on clipper files. But, OK, from what I checked out it's not at all hard to write my own *.el file, so I might just do it!

One another thing, a bit off topic, BUT I always use C-w to kill or M-w to copy region, is there some way to DELETE region(so it's not held in buffer)
(For example if I copy some text from another buffer or even another application I come back to emacs and if buffer is already filled with some information I have to kill it and then Control-yank and Meta-yank -> basically, I have to use three commands instead of two, first of which would delete region and second would yank previously copied region)

You should be able to use M-x delete-region, if I understand what you want (see, e.g. this). I just tried it myself and it doesn't store the text in the kill ring. Weird, though, as this command isn't in the manual :/.

Thank you, I should dispel my laziness of reading and take a look more into "GNU Emacs" documentation, because it is wonderful!

But that makes as human, that we can ask questions, get answers and learn from experience of others /Me/

The manual is pretty complete, yes. Also, Google is your friend!