About taxes, will we need to pay or submit something about the income from the books?

Yes. At the end of the tax year, or whenever you do your taxes, you'll need to report the income you recieved from KDP book sales. Remember that you are paid out 60 days after a sale. So for example, sales made in January would be paid out to you end of March. You can find reports of your payments and when they were made in your KDP Dashboard under reports.