When I'm walking to a nearby place, why the WiFi speed become very slow in a sudden?
Usually, it is because your cellphone still connects to the original place's wireless device. Since you are not far away from it, the signal become weak but still connected. This will cause the wireless network being unstable.
Solution: Please be patient and wait for the cellphone to automatically detect and connect to the nearest wireless device. Or, manually disconnect WiFi on your cellphone and then reconnect