Hello and welcome!

Quote Originally Posted by utku View Post
This Perfective/Imperfective things works same in English and Russian?
No, Russian Perfective and English Perfect are completely different things. There cannot be any direct mapping between them.

You can find detaled explanations on Russian verb aspect here:
Perfective and Imperfective Verbs - The Complete Guide
On Aspect of Russian Verbs
Remebering 'rule' for choosing aspect with negated verbs

Hope it helps.