Hi Lyudmila! I will correct your entry sentence by sentence. :) 

Y = you wrote

C = corrected version

Y: Well, do u know what happened with economy in russia (or russian economy?)

C: Well, do you know what happened with the Russian economy? (Don't forget your article 'the'!) 

Y: i will tell u, financial meltdown, but big (move?) part of russian people don't understand.

C: I will tell you - a financial meltdown, but a large percentage of the Russian people don't understand this. 

Y: They believe, that after few years,russia will be strong country,eternal illusion.

C: They believe, that after a few years, Russia will be a strong country. This is an eternal illusion. 

Y: This country is lagging behind for decades.

C: This country has been lagging behind for decades. 

Y: This country can't make good chair, actually in this country made nothing, only oil and metals

C: This country can't make good chairs. Actually, in this country, nothing is made. There is only oil and metals. 

Y: Russia with nuclear bomb(it may not even fly) believers citizens, and dangerous idiots with power.

C: Russia, with its nuclear bomb, which may not even fly, is full of naive citizens and dangerous idiots with power. 

Y: This country remind me poor country like irak,veezuela,but not so bad, not now, after 5-6 month it will be more close...

C: This country reminds me of poor countries like Iraq, Venezuela, but it's not so bad right now. After another 5 - 6 months, it will be closer. 

Wow! You are very hard on Russia! Personally, I love Russia, but I respect your opinion! I hope the economy there gets better soon. ;)