Two things to check. The first is about disonnects but has some suggestions that might help with slowness:
https://support.chess.com/customer/portal/articles/1444918
This one is geared towards live chess and Chrome or Firefox:
https://support.chess.com/customer/portal/articles/1444971-how-do-i-fix-slowness-in-live-chess-
If none of that helps, you might post what OS, browser and browser version you are using to help troubleshoot what you might be encountering.
My computer keeps crashing on your site. It shows very slow internet on my behalf even though my internet is fast. It could be advertizements, something with javascript because sometimes I cannot even move a piece.