It's not a direct answer to your question but nevertheless I think it will be helpful for you.
I think you will need some basic/advanced knowledge how data will be created, maintained, stored and processed within a "typical" company and how companies try to get insights in their data - only then you will be able to ask the first questions (to enter the game) and answers their first questions (to stay in play). This meant you need to know from own experiences how difficult it could be to produce valuable results from data which might be unstructered, have less quality or which are just extremly huge.
As a pure salesmen you didn't need to solve these cases (you need only to know the right people for this) but you need to know about the "standard" problems of your potential customers and you need to know how BI tools work and how Qlik worked (you asked this question within the qv community ).
A good starting point for this are books: Books and literature especially the first two book by QlikView and the first by Qlik Sense - you won't regret this investment.