You don't have a legally valid "Impressum" on fruits.de: It points to fanbase.com and that one isn't even mentioning fruits.de. So, as a German startup, it seems you're at least bending German and EU law by not providing the information necessary for proving services on the domain fruits.de. And as a result, as a potential user, I can't trust you with my business.
Moreover, I couldn't find information about your "sales tax" claim. You know better than me that selling digital products in the EU and across borders can be kind of tricky, depending on what you are selling (e.g. ebook vs software), if you're selling B2B or B2C, and depending on the origin of your customer. As a user, I'd need much more information about how you handle this and the bookkeeping you mentioned, but it somehow looks like you're relying on PayPal as the payment gateway and are not handling sales tax / USt by yourself?
And no: As someone looking for a simple solution to sell my digital products, I don't want do book a consultation for answers to the questions above.