Which PCIe slot to use for your GPU

16x is physical slot size, that is capable of wiring up to 16 PCIe lanes, but on your motherboard that slot has only 4 lanes connected to it

You could look at something like the C9Z390-series which have four x16 physical slots and one x1 slot

what is slot On the rear of the card is a full-sized 80mm slot, compatible with up to PCIe speeds and protected by an extra heat shield As PCGamer

what is pg slot The total bandwidth of an expansion slot depends on both the number of lanes and the PCI-e version, such that a PCI-e connection with eight