The internet gets slower when everyone is trying to use it, and evening slowdowns are one of the most frustrating examples. Just after work or school, many people in the same area come online at once, so your speeds can drop even when your equipment is working fine.
The most likely cause is network congestion. With cable internet, many homes in a neighborhood share bandwidth, which makes congestion worse. Fiber internet offers far greater bandwidth and is less affected. Wi-Fi also suffers when many devices compete for the same frequency bands, which is common in large apartment complexes with dozens or hundreds of devices.
Several fixes can help. Power-cycling your modem and router by unplugging them for at least 30 seconds forces the devices to clear their caches and reconnect, which may improve performance and is unlikely to make it worse. You can also create separate network names for each band and move data-hungry devices to 5GHz or 6GHz, which are less crowded than the 2.4GHz band. Reserve 2.4GHz for smart home accessories that need range more than raw speed.
Sometimes you will need to adjust your habits instead. Schedule software updates to run overnight, and avoid large downloads, torrenting or cloud syncs during peak hours. Postponing these tasks by an hour or two can be enough to ease the strain on your connection and on your neighbors' networks.
Source: Engadget · Summarized by HeadlinesBriefing