Welcome to the community!
Devices connected by Wi-Fi may experience slower speeds than those connected by Ethernet cable, have you tried to run a speed test using a desktop/laptop connected via LAN?
If yes, please post a screen shot of the speed test result.
Else, we did an article that will help you improve your wireless connection speed see the link below.
Easy Steps to Improve Wi-Fi Connection In Your Home.
Tell me how it will go.