Fatal error: Cannot declare class WP_Block_Parser_Block, because the name is already in use in /home/.sites/10/site3157514/web/newsite/wp-includes/class-wp-block-parser.php on line 15

Fatal error: Uncaught Error: Call to a member function set() on null in /home/.sites/10/site3157514/web/newsite/wp-includes/l10n.php:806
Stack trace:
#0 /home/.sites/10/site3157514/web/newsite/wp-includes/l10n.php(900): load_textdomain('default', '/home/.sites/10...', 'de_DE')
#1 /home/.sites/10/site3157514/web/newsite/wp-includes/class-wp-fatal-error-handler.php(47): load_default_textdomain()
#2 [internal function]: WP_Fatal_Error_Handler->handle()
#3 {main}
  thrown in /home/.sites/10/site3157514/web/newsite/wp-includes/l10n.php on line 806