Might not be ee or your router. Some older computers and phones just don’t play nicely with newer wifi. Do you have another computer you can try with?
Same with the two of you online problem. Some older machines won’t play nicely with newer ones 🙁 .
It’s a bit of a minefield and may be EEs fault but possibly not. If you are in an area with a lot of other wifi stations it can be almost impossible with cheaper gear
As scaredypants says though, the way to check is to use a cable with the router first. If that doesn’t work then the problem is likely to be the router otherwise it is the wifi
Then try with a newer computer to see if that fixes the wifi problem. If it doesnt then the problem is the wifi and I would add an external wifi access point (which I very often do)
It can also be worth using the inSSIDer program to see what other wifi is around as often you and your neighbours are all on the same channel as most people don’t change it. In that case changing the channel can make a big difference