Hi
shakza1223First of all, the speed of the Wi-Fi depends on the compatibility between the device and the router. You can also check on the spec of both. Furthermore, kindly provide the information below so that we can better assist you.
1. Your current firmware version
Settings>System>About Phone>Software information
If you try to update to the latest version, does the issue still persist?
2. You router model
3. Has the router ever changed before?