Hi Iram, 

Happy to provide a perspective.

1. What are the possible causes and the Solutions? What kind of structure/framework that I can use?

One way to look at it is to start from the clear, quantifiable target they have and then break it down into drivers that would help generate that impact. 

This is one way, of course, and there are many, many others. 

Feel free to suggest some as well and I'm happy to provide some feedback. 

2. Since, they dont share data, what kind of quantitaive information I should look into?

It depends on the sort of questions you come up above in the framework, but I would look at least into a segmentation by customer type and product. 

3. Any website that I can learn from regarding ecommerce industry? (beside ecommerceguide)

It might be easiest to go to ChatGPT and ask it to generate it you crash course with several core articles to read for more in-depth analysis. 

Best,
Cristian