Wifi realy slow until I turn on Low Power Mode

Hello everyone. I recently bought my First iphone, but i am having problems with it…

So whenever I connect to my home wifi, it works well for a few seconds but then becomes so slow that it cannot be used for anything while mobile data is super fast all The time. Normally this gets fixed when i turn on Low Power Mode, then everything works fine. But I don’t want Low Power mode to be turned on al The time nor to factory reset my phone… does anyone know any solution for this?

My iPhone uses iOS 14.7

Things i’ve tried:

-reset network settings

-change DNS servers

-restart phone