If you do not have a backup will be very difficult to restore your website since backend is no more accessible, my suggestion (after you backupped all your website files) is to install on local an older version of joomla that was correctly working ( maybe 3.8.3 ) then copy via ftp on your website only joomla folders to overwrite your new version installed with old joomla files, do not override confoiguration.php file it contains database info and other settings that shouldn’t be overrided.
Problem solved. I download joomla 3.8.5 unzipped it and deleted the installation folder and the other files leaving the remaining folder. After that I zipped it and uploaded it to my cPanel and unzipped it there. Went to the backend and front end and everythg is back like before. After that I updated it to the latest version 3.8.6. Problem solved. Thank you Pavit
This reply was modified 5 years, 8 months ago by djalloh1005.