Site is never closed. If site were to be closed we would all be redirect towards a 404 or a landing page.
If site is very slow it's either your internet speed or your computer memory.
Internet Speed: If it's your internet speed then you're probably downloading too much or too many devices are connected to your internet and utilizing it.
Computer Memory: Usually happens when you've a lot of programs open and your browser doesn't have enough memory for it to load pages hence sometimes taking forever to load.
Solution to both would be to not have several tabs / programs opened up and make sure your internet isn't being heavily utilized.