Mayrl,
From your post, it looks like the very beginning of "requirement gathering". At this stage, the questionnaire should have broad, with open questions. Subsequent questionnaires, meetings with go in to more detail - step by step.
1. What is the business? manufacturing goods, service, trading etc.
2. In what countries is this business?
3. What are the main business processes?
You can look to group these processes in terms of Sales to customers, Non-sales processes
4. What products do they sell?
Not much detail - your aim is to get the important groups of material
Are these expensive or inexpensive?
5. Who and how many customers?
In summary, for this interaction with the client, your objective is to get basic idea about 3 things -
- Business processes (that later will manifest in to process design - sales doc types etc. etc.)
- Master data (material and customer master data)
- Basic functions (output, text, credit, partner, availability check, TOR etc. etc.)