Here are the steps to switch back to Office 2013:
1. Use the Fix it tool to remove the current Office 2016. See:
Uninstall Office 2013, Office 2016, or Office 365 from a Windows computer
2. Install Office 2013 via the URLs below:
For Office 365 Business or Office 365 Business Premium:
32-bit, English:
https://c2rsetup.officeapps.live.com/c2r/download.aspx?productReleaseID=O365BusinessRetail&platform=X86&language=en-us&version=O15GA&source=O15OLSO365
For Office 365 Enterprise E3 or Office 365 ProPlus: