Since you've replace the router, we can rules that out as the source of the problem. Since the wired connection is affected, too, that riles out RFI.So the problem is in your modem, the phone line or TV cable to your house, or with your ISP.
The problem: How long does it usually take you to set up your router? When was the last time you were able to get it right on the first try? What about when you wanted to add a new PC to your wireless network? And how about getting your wireless printer to connect to your network?
Let's face it: Each network is different, and getting the right combination of settings can be confounding. For example, even some reasonably experienced PC hands may not understand the differences between security settings or know that WPA-2 offers better protection than WEP and ordinary WPA.
Restating a router is really easy as you need to check for https://www.router-reset.com/router-login-web-interface/ASUS to get to see how it's look like and what you need to do. Nothing that a regular teenager can't handle, not talking about an adults one tho. You can do it, trust me.
I think you should find instructions to your router and find there all the information you need. Personally, I decided to buy ASUS AC 1750 and I had all the information about it in the instructions. Or you can call the hotline, this is up to you