Hi Muhammed,
What channel-width is used, how many spatial streams is support on client and ap, what signal-strength and SNR the client have, any interference sources.
Please note that the wireless-connection speed is shown in your network adapter is the 802.11 (Wi-Fi) modulation rate. When it says a connection speed at 866Mbps this is the modulation rate.
Due the large overhead of a Wi-Fi frame (802.11) your real speed at the ethernet (802.3) will be approx. 50% of the modulation ratie.
So if your network is about 866Mbps, your speedtest will about 400-500Mbps real download speed.
Also note thate Wi-Fi is sensitive for air quality (airtime utilization) and some interference will give you an "x" percentage of acceptable re-transmissions.
You can check the MCS index for the right Wi-Fi modulation rates and keep in mind that approx. 50% will be your ethernetnet download speed. Link
https://mcsindex.com/Hope this helps!
------------------------------
Marcel Koedijk | MVP Expert 2022 | ACEP | ACMP | ACCP | ACDP | Ekahau ECSE | Not an HPE Employee | Opinions are my own
------------------------------