asrock h310m-hdv/m.2

Hello, I'm having an issue with my read/write speed on my m.2 samsung 960 evo. My read speed is only 1750 MB/s and write 700 MB/s. I'm aware there are tons of solution and threads on this subject, but I can't make sense of them nor find my answer. I'm not sure if it 's some sort of PCIe...