We've developed the first version of our website and going to lunch it and introduce it to a crowd. How do we know which part of our work has weakness and how we should correct it?
If I had to rephrase your question, you are trying to understand what part of the website were people able to understand, which parts were they not. Sure, analytics, heatmaps etc will help you a lot with it but nothing is better than actually talking to some people. This could be over chat where you could ask people if they understood what the service was about but is best done over call - I don't know your business to tell you how to get people on call but nothing beats the density and richness of information and surrounding context you can get when you get users on a call.