If the game is slow or crashes try to put the quality of the game down. To do this you will find at the top right side of the game an optionsbutton in which selecting HD you will lower the quality to increase the speed of the game.
We also recommend:
Close the maximum number of windows/ tabs you have open especially when these are download programs.
Check your PC with an antivirus and antispyware to make sure that there are no malicious elements and that the antivirus is not blocking games. For more info click here.
Make sure you have installed the latest version of your browser: Google Chrome, Mozilla Firefox, Internet Explorer... and of your OS windows, OSX, etc.
We recommend the following steps:
First of all delete the search history, cookies and cache of your browser and try again the game. You can see more information about delete the cache of your browser here.
Check that you meet the minimum requirements to play.
Uninstall Flash Player. On Windows you can do it from “Control Panel-> Add or Remove Programs”.
Restart the computer.
Install Flash Player.
Check that Flash Player works properly (you can see the version you have installed).
If you continue with problems after installing try accessing with a different browser. Sometimes there may be incompatibilities between certain versions of a browser and a plug-in.