There are many reasons, there may be router reasons, there may be other reasons, in general, the common reasons for slow network speed are the following: 1 wifi by people, others occupy the bandwidth or give you the speed limit, you can log in to the router management page to see the number of connected devices.
2. The performance of the router deteriorates after long-term use. In this case, you can restart the router or restore the router to factory Settings.
3. The wireless signal is not good, you can try to stay closer to the router.
4. The terminal equipment (mobile phone, computer) itself