Some network operators will adopt DNS hijacking methods to interfere with users’ normal Internet access. This will cause your internet speed becoming very low.
1.One solution I ever tried is modifying the DNS address of wifi , that’s useful for 2G/3G/4G/wifi network, example the google Dns address is ‘18.104.22.168’, you can have a try.
2.And also, I will give you the 2nd way if you are willing to take the risk, you can think about modifying the dns file, now just open the file /system/build.prop, and add these codes behind the last line.
Then, you should reboot your phone, and Best wishes!!
3. In addition, there are generally some APPs in the software store to enhance the wifi signal, but this kind of software actually does not work well, and will not bring great improvement to your wifi network.
And there are many factors that affect the WiFi speed. I ever wrote some articles on this topic before, I hope it can be useful for you,