Q: Business model and customer needs

Sorry?

The case very explicitly states the the business model as such:

"The interviewee should understand here that the core product of online marketplaces is connecting demand and supply and thus generating fee revenues. In addition, he or she should also find out that almost all online business models generate revenues with online advertising."

Furthermore, you do not need to know competitors + customer needs:

Remember, in a case you need to focus on what matters. Again, the case explicity states in the case prompt:

"The market environment has already been examined in detail – competitors, new entrants, customer needs, etc."

"As a result, you are asked to identify growth areas and to quantify the potential sales uplift for the management."

This is very straightforward! They've literally told you "don't worry about competitors/customer needs...please focus on growth areas + sales uplift"