Nearly every Wi-Fi complaint we hear at the bench arrives with the same story: it works in the morning and falls apart around four in the afternoon. People assume the internet is rationed. It is not. The router is drowning.
By late afternoon every apartment on your floor is streaming something, and consumer routers ship set to the same crowded channel out of the box. Everyone is shouting on the same frequency at the same time. Your router is not slow. It is polite, and being talked over.
The fix takes five minutes and costs nothing. Log into the router, find the wireless channel setting, and move the 2.4 gigahertz band off auto to channel 1, 6, or 11. Those three do not overlap. Everything else does, which is a design decision someone should apologize for.
If that does not do it, the router may simply be old enough to vote. But swap the channel first. It is free, it is reversible, and it fixes the four o’clock slump more often than any gadget a store will sell you.