Wi-Fi works incredibly slow on iphone, but fine on other devices. What will

My phone works incredibly slow when it is connected to my Wi-Fi. I can't load youtube videos, Facebook or any other social media apps/websites. They sometimes load, but take forever that I just use LTE data. A Wi-Fi extender did not resolve this issue. My laptop and TV connect to the internet fine and all of my roommates don't seem to have this issue. Are there too many devices connected to the Wi-Fi (my two roommates have their phones, computers, TVs, and printers connected)? Is it just a problem with my phone? I checked the IP address and everything. I pay the Wi-Fi bill and it sucks that I can't even use it. Any tech-savvy people know what will help?

Unidentifiable Bluetooth users connected to my iPhone?

Only when at home, I find 4 unidentifiable Bluetooth users "connected" to my iPhone. Because the id is longer than space provided, I do not have the option to delete, because there's no lower case I in a circle icon.
How do I disconnect and delete these strangers?