Good question. It either creates an usual situation, like a shop owner who likes to hire someone else to manage while he takes care of sales, or it's an issue of translation or interpretation. Why would anyone use "shop assistant / sales clerk" to translate Verkaufer when it's the actual owner. The best translation, overall, I'd say would be "salesperson."
Or, the American "sales clerk," being less a subordinate position, simply refers to a specific sales clerk who is not only the senior one, but is also the store owner. The question then for the Brits would be, is shop "assistant" much less emphatic on that part of the word through usage, so that it's meaning is actually more in the sense of a salesperson in a store?
Or else it could be a co-operative shop, in which several shop assistants / sales clerks are actually ALL co-owners, and that's my favorite answer.....!
Even if the shop owner hires someone to do most of the work, that person is still, by definition, assisting the owner, since the owner is in charge and is fully responsible. The owner can order the person to do the work, which an assistant can't do. And the manager can't order the owner to do anything, even if the manager has full responsibility for operations.
If there were such an arrangement, the manager could fire the owner, who would go back to being the manager's boss.
Regarding all the comments here: "Verkäufer" also could mean the person who is sitting in the counter currently (although the exact word would be "Kassierer"). So this sentence makes sense e.g., in a small town where somebody is doing the cashier job and then a friend is telling to a visitor: "The cashier owns the shop(, by the way)".
The seller = der Verkäufer The owner of a shop is called “the manager” , in German: der Manager and in Dutch: “de gerant” Why using in German: der Verkäufer? and not “der Manager” ? In big shops or Supermarkets the owner is a company with a general manager and above him the share holders. But the word “shop assistant” gives me the impression that in this shop only is working one single person....
the hints state that seller or shop assistant is the correct translation for Verkäufer. I have reported that if it will do any good. 2nd how can Verkäufer mean both shop assistant and shopkeeper. how can one tell the difference if it is the owner who owns the store or the assistant who owns the store?