Wifi doesn't work

When I connect to wifi it says it has a connection but when I try to open safari it loads forever.

The problems always happen, I can connect with internet with my Ethernet cable but not with my wifi.

The web page loads like 15 minutes and than there is a notification that there is no internet connection available..

It happens all the time, and I do use a router but the wifi does work on all the other devices; iphone, ipad, other macbook, imac, pc etc

This problem started like 2 months ago and before that, I never had a problem like this

It happens with all browsers and mail and everything