Yes. You can pay the courier in cash or by card, but there's a service fee of SAR 22.5, which you don't get back even when the order is returned. Your order has to be worth at least SAR 100 and no more than SAR 1,875, and has to qualify for free shipping. When an order is split across several shipments, the fee is shared between them.
Bear in mind that returning something you paid for on delivery won't get you cash back: the value goes into your Trendyol Coins balance instead. If that doesn't suit you, pick another payment method from the outset.
Source: Trendyol Help: payment