Scenarios based interview questions. how to approach it and clear the interview

Hi! All

I am Deepak and I am a User Experience Designer(deepakraj.in). Recently I attended two interviews recently, I was given scenarios and they asked me to come with design (wireframes), flow chart or mind map, task analysis.

Question 1: David is a milk vendor and he wanted to start a business online. He is technical savvy guy. He handle latest gadgets. He should be able to take daily reports and serve the milk to customers. And customers are eager to place orders online service. Create a system where David could handle the volume of customers. Remember the happy customers are who David interacts in his daily life, serving milk at thier doorsteps.

Question 2: Daliyfresh is a new organic fruit vendors shop started in local. The owners want have hired five people to look after the shop and they want sell their fruits in the local market and sell more fruits and compete with gaints like walmart, target and other big vendors. Create a system where the Dailyfresh owners can run their business and compete with the bigger vendors.

I struggled in both the interviews. So, how should I begin the test and how should I prepare my task analysis and how should I begin the wire frames and flow chart/mind map.

Please help me. So that I can clear the exams