There may now be a different issue. This challenge, as it's a bit differently coded I think, isn't slow. It'll work quite well; for me, I passed it in a second or so.
I'm going to make an educated guess it's likely extensions or browser settings. Change those so things work, and you should be set! Do let us know if that helps out.
P.S. Heading offline soon, but others may be able to help out, and I'll be on no later than tomorrow (Sun.) probably later today.