Hello!! would you be so kind to tell me, on what sites can i find information on informal (colloquial) style of English?
Welcome to the forums.
This is one that is quite interesting: The Dictionary of Informal, Colloquial, Slang and Idiomatic Phrases in Spoken English By Hakan Senturk.
PLABWISE™ - Making PLAB Easy
An ELT Notebook: Colloquial English : Expressing Emotion
You can always post questions here and someone will try to help.