CRM 2015 online performance issues

Hi,

We are using Dynamic CRM 2015 online and having performance issues like

1."Internet explorer is not responding", 

2.An error occurred.Try this action again. If the problem continues, check the Microsoft Dynamics CRM Community for solutions or contact your organization's.Microsoft Dynamics CRM Administrator. Finally, you can contact Microsoft Support. 

how can we over come these issues. Thanks..