Even the TV doesn’t work
So it’s probably not a configuration setting that is a problem if the TV was faster but now isn’t.
Start with the basics, has the router/modem been restarted yet?
If so, can you connect a PC/PS5 with ethernet and see how speeds are to narrow down if it’s a speed problem with the Wifi vs a speed problem with the whole device?
If it’s just the wifi, honestly, just factory reset it if your parents are okay. Then put your network name and password back on. Modern devices are pretty darn good at auto-negotiating their channel settings and things like that.
If there’s a speed problem even over ethernet, you might have an ISP issue, or the device itself is failing, or someone tripped over a cord and yanked it loose.
Could be a million things, so focus on narrowing down what exactly is not working
Sounds like something isn’t shielded properly. Either by design to save costs, or as a defect. Could be your mic, could be the jack on your PC. If you’ve had other mics without this issue, then it’s probably the mic.
Honestly, nothing you can do to ‘fix’ it aside from replacing whichever component is faulty. You might be able to shield it with aluminum foil around that port.