WiFi on phone super slow

[AC Question]

I am using a lenovo s898t+ phone with a resurrection-remix 13.0 ROM on it(it is android 6.0.1) My home WiFi is super slow, but it only is when i connect to it with my phone. Any other device is fine. I get access to internet through tethering the WiFi through my laptop(connecting, and setting up a hotspot) IDK if im gonna be able to answer any questions on this thread, because the website for some reason is not letting me create an account. Also this has happened before, stayed for a little bit, and went away. I have tried turing the router on and off/ plugging it out for a whole night. I have not tried factory resetting it, but i will soon. I really need help.