@Rab 

Hello, please help verify some details and we will try to fix it together:

1. May I know who is your ISP? What are the download and upload speed you can get when you connect a computer directly to the modem? Kindly show me the test results.

2. Without any devices connected, please connect one computer to the WR720N directly and go to speedtest to run the test for 3 times and show us the screenshots of the test results.

And please tell me the wired link speed at that time, how to get that? You can refer to the below link.
https://www.tp-link.com/en/faq-2265.html

3. You can refer to the below instruction to narrow down the issue as well.
https://www.tp-link.com/en/faq-2170.html

Good day.