Can I put a PCIE X8 GPU in a PCie X16 slot?

I was told by tech support that the motherboard has 2 PCIe x16 slots and that they run at x8 speed I found this out when i was inquiring as to

Can I put a PCIE X8 GPU in a PCie X16 slot? Delock Riser Card PCI Express x8 to x8 with flexible cable 30 cm Item No : 85766 88029 Delock Riser Card PCI Express x8 male to x8 slot with cable

I was told by tech support that the motherboard has 2 PCIe x16 slots and that they run at x8 speed I found this out when i was inquiring as to

pcie 50 slot For instance, you can place a PCIe x8 card into a PCIe x16 slot when the PCIe x8 slot has been occupied, but that card will always run in PCIe

as you have a Non G Processor that top slot should be running at full x16 speed the Top is coming Directly off the Last 4 PCI-E lanes

pcie slot size For example, a slot might be described as x16 physical, x8 electrical The physical size literally determines the size of the slot on the motherboard You can

Btw, I'm pretty sure it's on the correct slot and I do not have any NVMe on the M2_1 slot or any at all for that matter