How many units will i need for 8th vilage if for 5th i need 100, for 6th 200...
and one more thing why i get mesage response eror when i try demande resources from farming vilage?
This information can be found on the wiki, here: [wiki]Farming#Conquering_Farming_Villages[/wiki]. Its not a bug, but rather an incentive for people to build troops.
The response error will appear when there was a miscommunication between the server and your computer. If you wait a minute and try again it will clear itself up.