An approximation will do, just getting a sense
Simply skip this page if you don't have an existing site.
Leave blank anything you don't know
If you're selling to businesses, think about your usual contact person in the business
A "sales funnel" is business-talk for how you convert "anyone" to "interested people", "interested people" to "customers" and "customers" to "fanatics". Some people like a strict process, but even if you don't it's good to be able to talk about the activities you do at each step to progress people from one stage to another.
Your website can help with several funnel stages, but does its best work around the middle of the sales funnel.
Yes, it's important to focus on just one. Usually it's edication or sales.
Needs after design: