d_lokesh989
If you feel like you are not confident in this then ask your local wifi provider for support this info is purely based on my experience and I had help from my local provider
Open a Web browser and Type your routerâs IP address in to the browserâs address bar.Hit Enter after you type in the IP address (example: http://123.456.1.1)
Your browser may display a warning screen at this point, then Click Proceed.
Most routers have a sticker on them that shows information such as the routerâs IP address (shown as Router login details)and the username and password you need to log in to the router
Enter the username and password exactly as they appear. They are case sensitive.
If youâre having trouble finding the username and password, check the documentation that came with your router or contact the router manufacturer.
Then follow this link to change only the channel width to 40Mhz
https://www.tp-link.com/us/support/faq/2292/
*Please note your interface might not look like this since itâll be different internet distributers