After updating wordpres, this error will appear at the top of the page. I also cannot log into wordpres as administrator and restore the backup. I do not know what to do
DEPRECATED: The file wp-db.php is deprecated since version 6.1.0! Use wp-includes/class-wpdb.php instead. In /home/fundacjakrol/ftp/fundacjakrolestwo/wp-includes/functions.php on line 5595
Warning: Unable to modify header information - Sent started by output in /home/mysite/ftp/mysite/wp-includes in /home/mysite/ftp/mysite/wp-includes/functions.php:5595 of headers/functions.php line 6865
Tried removing all plugins but that didn't help. So it seems the problem is with wordpress itself.
Search wp-db.php in the template file and replace class-wpdb.php