Every time when I am typing the code into the editor my browser is popping up an error, that this page is slowing down my browser.
Have you tried swapping browsers to see if the problem continues?
Sounds like an issue with the browser as oppose to FCC itself. Either way if you are able to provide some kind of screenshot and try to open FCC in another browser to see how it operates, members of the community should be able to help narrow down the problem.
clearing browser cache may possibly help here also
So, I tried it in edge and firefox again, and I’ve noticed that pages crash when I am closing the bracket for the @while loop.