Not able to chat with my company's contacts and all my company's contact show as external contacts

Hello @sokh,

Welcome to the Zoom Community! We're glad to have you here.

It seems that you are not a part of your company's organization, I would recommend reaching out to your IT department or Zoom admin.

For the hanging part, kindly update your Zoom app to the latest version as well as your software drivers. 
We would also advise closing other applications while using Zoom that might be stressing your CPU usage.

If you need further assistance, please let us know.