Catalina problem with Wifi

Hey everyone,

I updated my iMac (somewhere around 2013) to Catalina last week. Since then I am somewhat unable to connect to webpages. My Mac says that I am connected to a WiFi network and when I open Safari, my homepage (the Apple website) seems to load up (a bit slow though). But then when I try to open a simple website like Google, it might take forever to load or sometimes says that it is unable to connect to the server. The same problem occurred when I tried to make a new user. During the configuration of the new user, I tried to log in with my Apple ID, but after a while of loading it gave the error message: Cannot connect to the Apple server.

I tried all the usual things to fix this problem I could find on Google. Even tried to solve the problem the way someone else mentioned on this forum (by changing some stuff in the system preferences > network), but nothing seems to work.

Does anyone else has this problem, or knows how to solve it? It would be much appreciated! :)