The problem with most people are not that they are stupid but more to lazy to structure and setup their business correct.
You want to get a professional website setup which is reflecting the fee structure of your "hidden" business. If you are unable to do this task yourself then find a professional webdesigner to make the website for you. Next things is the business description and even a business plan. If you can provide both in professional English and which explains your "new" business activity in a professional language your chances to get a bank account rise by 80%.
The final step is to︀ generate invoices each time you sell something, if you produce many each day you need︁ someone to build a system for you that do this automatically, if you only generate︂ a few invoices a week you need to do the task manual and find a︃ professional accounting system to do the task. If someone request a particular invoice it looks︄ way better and professional if you can deliver the request within minutes.
that's just a︅ few hints, hope it helps for a better understanding!
