Update Drupal Core manually

This is how to update Drupal Core to live server:

1. Update modules or themes
2. Backup files & database
3. If you make manual modifications to files like .htaccess, composer.json, or robots.txt - copy them somewhere to re-apply.
4. Put the website to the maintenence mood
5. Don't touch the modules, profiles, sites, themes, Libraries
6. Optionally sometimes an update includes changes to default.settings.php or default.services.yml files. 
   * Make a backup copy of your settings.php file, with a different file name
   * Make a copy of the new default.settings.php file, and name the copy settings.php (overwriting your previous settings.php file)
   * Copy the custom and site-specific entries from the backup you made into the new settings.php file. You will definitely need the lines giving the database information, and you will also want to copy in any other customizations you have added.
7. Remove the top-level files, core & vendor
8. Upload the files form top-level, core & vendor
9. Reaply (if related) the change in step 5
10. Using your browser, run update.php
11. Check status report to make sure everything is fine
12. Go to Maintenance mode. Uncheck the "Put site into maintenance mode" checkbox and click on the "Save" button.
13. DONE