Please mention you WiFi device so the solution can be provided accordingly.
If you are using a router of any brand, you can apply such limit in the settings by log into the router.
If you are Huawei Enterprise user, you can modify the profile on the OLT to change the bandwidth of the ONT by referring to the preceding method. ecause The ONT does not support bandwidth control. You can limit the bandwidth only on the OLT side.