MOTIVATION
Chances are, you'll be asked why you are leaving Russia, and what made you apply for immigration specifically to Canada. Here are some possible ways in which this essentially one question can be phrased:
Why are you leaving Russia?
What is your motivation?
Why have you applied for immigration to Canada?
What do you expect Canada to be like?
What is your destination in Canada?
What do you expect to achieve by relocating to Canada?
What are your plans for Canada?
What do you see yourself doing in 10 or 15 years from now?
My advice is to start by giving an unedited "true" answer. I am speaking, of course, of the preparation, not of the actual interveiw. Then edit out the low-spirited motives such as how hard life is in Russia, on how poor and tired of it all you are etc. To be more precise, edit these to sound more upbeat.
For example,
I can't make enough money to support my family. I am a researcher, and research pays very little. And things are not likely to improve in the nearest future. Life is so much easier in Canada.
becomes
I am dedicated to my profession. In Canada it pays enough for me to easily support my family, and to concentrate on my work. Natuarally I am not happy to leave my country, but everything considered, I think we are doing the right thing.
Please also look at the "language masochism" exercise. And the main Questions and Answers list and whatever other materials you can find here.