Dear @PooriaT,

i have a TP LINK modem/router model TD-W9970 which i am not happy with that, but wifi works slowly(at least) and other devices woks with Lan.
I tried two unmanaged switch in one room and none of those works properly. i reject the first one and now i have a tp link unmanaged tplink tl-sg1008d.
so one cable from my router goes to this one. ps4 work properly but my pc and my tplink access point couldnt get internet. it said something about dns issue.

The TL-SG1008D is just an unmanaged switch, which is mainly used to expand the Ethernet ports of the router or LAN network. There is no configuration required or supported on the unmanaged switch.

Where do you see the error message about dns issue? Could you provide some screenshots for checking? If your PC cannot get Internet through the unmanaged switch, please check the IP info on the PC for analysis, here is a guide about how to find IP address on the PC for your reference. https://www.tp-link.com/support/faq/838/

In addition, if you hardwire your PC and tplink access point directly to the TL-W9970 router with LAN ports, so remove the unmanaged switches, can you get Internet access on the PC? Do you have Internet access after you connect to the WiFi of the access point?