Niko doesn't speak Russian, he speaks Serbian.
Just speak Russian like you would and do it with English. Mimic the diction and the grammatical structure.
stop being an ass 2worlds
just get american videos that are related to soviet russia, get games that involve soviet russia I advice you with C&C red alert" , WW 3
listen to their speech, mimic
after a while you will be able to do soviet accent which is russian
if you still cant make a russian accent, and your russian you just fail at life, in a epic scale