Expected turnover per month

Dear Ibendlin,

Thank you very much for your response and your request for a data model.
I had created a small set of data with Excel to show what I would like to have in PowerBI.
Unfortunately, it appears not to be possible to upload an Excel file. I then tried with a table, but it became more than 20,000 characters. Is there perhaps another way to send it? 

The expected turnover is always invoiced on the last day of the month, so the entire monthly turnover can be booked on the ENDOFMONTH. The first month in which the customer will be invoiced is therefore only a part of the entire month.
Hopefully, based on this information, you have a good tip for me on how to tackle this in various steps.
Thank you very much in advance.
Kind regards,
Hans