There are two ways to see your receipt. 

In app

Go to the 3 lines at the far right. There you can see your subscriptions, receipts and what is unpaid.

In browser

Go to the website you bought the course/training fee f.x www.sportabler.com/shop/"nameoftheclub"

Login at the top right corner and in the top right corner you can see my invoices and my subscriptions. In my invoice you can download the receipt in PDF file.