Windows 10 version 1803 problem

I ran W10 version 1803 update two days ago.  I have updated an excel file but when I saved it the file was unchanged.  Major problem.  My backup copy of the file had the same problem. So I uninstalled the update (took more than an hour).  My PC has now downloaded 1803 again and is asking me to restart.  How do I prevent it doing this.  I am using MS Office Student and teacher edition 2003.