Why the wait is the problem
Someone buys a preset pack at eleven at night. If the file arrives in a marketing email an hour later, they have already messaged you asking where it is. Digital buying is impulsive and the patience window is short, which is why delivery speed matters more than the storefront design.
Set the file up once
Attach the file to the product and the delivery happens on every order without you touching it. Use a clear filename with your name and a version in it, because that file gets saved and reopened months later on a different device.
If the product is access rather than a file, a key or a link works the same way. Whatever the buyer needs, it lands in the thread.
Keep a receipt the buyer can find
The chat is the receipt. That is an advantage over email, where your message competes with everything else in an inbox, but it means the order confirmation should say clearly what was bought and what arrived. A line naming the file removes the question later.
Stars for digital goods
Digital products can also be sold for Telegram Stars, the in-app currency. The buyer pays with Stars inside the chat and the Stars land on your own bot balance, so nothing sits in the middle. It needs no payment provider and no card processing, and it is available on a paid App plan with your own bot.
What to prepare before launch
Test one purchase yourself from another account and read what arrives as if you had never seen it. Most first-time digital shops send a perfect file with no sentence explaining what to do with it.