What is slow? The internet connection? Or the phone itself? Need more details on what's actually going on.
Try thisSeems to be the internet connection but the reason is because it falls back to cellular 4g lte/5g for no reason.
Yes I have a good router and really good internet (fiber)
Nope didn’t work already tried sorryTry this
Go to Settings, Connections, tap Wi-Fi, tap the three dots on the upper right, Intelligent Wi-Fi, then disable “Switch to mobile data”.