Netflix slows down Wifi in the house, but not Ethernet, how to fix this?

[Bencuri]

I know it is not a networking forum, but at least here I know there are people with intelligent way of thinking, unlike at Quora or Reddit. So let me know if you have a suggestion:

I have a problem since my mother purchased a Smart TV this year: when she's watching Netflix, the Wifi seriously slows down for every other device in the house. Moreover, during this time, the Netgear signal booster on the second floor is very often unreachable, that is just so odd, as if it was switched off. At the same time, however, if I connect a device, like a laptop with ethernet cable to the internet modem, the internet will work like charm again, both on the TV running the Netflix and on the Laptop as well. What causes this and how to solve it? I cannot connect the TV on Ethernet. Maybe purchasing a better router? I am using the old Technicolor internet modem that my provider gave us a decade ago.

[TreeTops]

" I am using the old Technicolor internet modem that my provider gave us a decade ago. "

I suspect that is your problem.