Failed update: What to do if WordPress update failed
In some cases, the automatic update via the built-in update management fails and you only see one error page or one White side. In such cases, there is not much left but Manually update WordPress.
Before you start, it is very important that you download a backup of all files on your server (via (S)FTP) and create a backup of the database (via PHPMyAdmin). When backing up the server, pay special attention to the folder WP content, as this contains all the files you have uploaded and adjusted. Everything else should correspond to the WordPress standard and can therefore be replaced by the new WordPress version.
Once everything is backed up, you can update WordPress manually. To do this, you must first Download WordPress – You can find the current (German) version at de.wordpress.org/download. Unpack the ZIP archive on your computer into the wordpress folder and delete the wp-content subfolder there.
Log into your server using an (S)FTP program and switch to the WordPress root directory. Now copy the contents of the folder to the WordPress root directory on the server – your FTP client will ask if you replace all files want. Confirm the process to start the upload.
The upload can take a while – if it aborts, upload all files again to be on the safe side so that nothing is lost. After a successful upload, all WordPress files are now up to date. Now try whether you can log back into the WP Admin interface via your-website.de/wp-admin. If that is possible and the errors no longer appear, you have WordPress repaired successfully.
Note on plugins / themes: Since you excluded the wp-content folder from the update, no plugins or themes were rolled back. So if a failed update of a WordPress extension is responsible for the error, the manual WordPress update probably did not change anything. In such a case, you must manually delete extensions using (S)FTP on your server in the wp-content folder under plugins or themes. If you know which plugin or theme failed to update, it’s best to start there. Always delete a plugin or theme folder and then test if that worked. You can restore too many deleted files at any time from the previously created backup. You can also re-download all free extensions from WordPress.org.