RE: Learn Dynamics 365 by actual business needs.
Hi Anthony
Firstly you may benefit from passing the certifications which relate to functional areas of Dynamics 365 Customer Engagement. So sales and service.
These exams are MB2-717 (Sales) and MB2-718 (Service). I provide some revision material here …
neilparkhurst.com/.../mb2-717-certification-microsoft-dynamics-for-sales-revision-guide
neilparkhurst.com/.../mb2-718-certification-microsoft-dynamics-365-for-customer-service-revision-guide
Although I think your question possibly goes deeper than just theory!
Learning the theory on how Dynamics 365 "should" be used is important. But applying to real-world scenarios is a different level of challenge. You mention "medium sized company". Unfortunately in my experience the size of the company does not always reflect the complexity of the requirements. I have worked with some very complex small companies and some really simple large companies.
A good start point is often to use a standard approach to document the "as is" and "to be" processes. What does the company do now and what would they like to achieve?
Unfortunately how you actually use Dynamics to deliver the "to be" will vary with every customer. My advice to customers is always start small and let the system grow overtime. Try to look for business requirements that are very close to the out of the box solution. Implementing those first will help you learn more about the customer's requirements and also give you (and the customer) valuable insight into how to tackle some of the more complex requirements.
FYI … your question certainly isn't stupid. (far from it.) But it is very broad. I suggest working with your customer on possible requirements. Maybe then you can ask some more specific questions.
Hope this helps
Neil.