I need help with my var partition.

[Maureen L Thomas]

I am 72 and have forgotten a few things.  I looked up debian/var and was 
told I could delete /var/log/

and /var/tmp/ and /var/cores/.  I left cores alone and deleted the other 
two.  Now I cannot burn a backup, download files and even go to web 
sites from my nord vpn which was working great until I deleted the above 
files.  I really want to upgrade to debian 11.  I am using debian 10, on 
a Lonovo all in one and have had no problems.  I followed the directions 
for var that I found and now have a screwed up machine.  Is there any 
help available. I was thinking of upgrading online but don't want to 
loose my data.  Please help this old lady.