Slot lanes 16x or 8x Using a PCIe M.2 expansion card

Howdo all,

I was just wondering:
I have an Asus Prime x370 Pro running Ryzen 7 1800x

I have seen in my manual for the mobo that if 2 x PCIe /VGA cards are used then the PCIe slot 1_16x will go from 16x to 8x and the second PCIe slot 2 or 3 will also be 8x

If i have one 2080Ti (which i do) in slot 1 at x16 lanes, but if i add a PCIe to M.2 expansion , will this reduce the GFX card lanes to x8? As the mobo only accepts 1 x M.2 slot,so thats my main runner for...

Slot lanes 16x or 8x Using a PCIe M.2 expansion card