Sale of second-hand goods from private persons on commission

I see two ways that both seem correct:

Either you purchase the products from the private person (expense) and then sell them (income). You then pay taxes on the difference between the two (profit). The purchase price you paid to the private person is then your selling price minus your commission. On the other hand, you could simply say that you provide services to customers and that the product never becomes your property. You then only create an invoice for the commission you receive on the product. That commission is then a kind of wage for the services you provide.

The biggest difference is in the turnover you generate. In the first scenario, you have a much higher turnover because you first make purchases of all those products in order to sell them. In the second scenario, you do not have any trade goods of your own. You only sell the services and therefore have a lower turnover.

Dear Sir/Madam,

My apologies for the delayed response.
Thank you for your help. In the meantime, I have received the same information from other people and an accountant.
Only in the second scenario was I stuck for a moment on how to deal with the cash flow (if I have received the total amount and I have to transfer it minus the commission to the private seller).
But I have been told that as long as I have a statement for the transactions on my bank account, I would be okay with the second scenario.

Thank you,
Kind regards, Marcus