Fix the 500 critical error on the WordPress website

My WordPress website is currently displaying a 500 Internal Server Error and is completely inaccessible to visitors. This is critically affecting my business, and I need an urgent fix. I am looking for an experienced WordPress developer who can quickly diagnose the root cause of the issue, whether it's a plugin conflict, a corrupted .htaccess file, a PHP memory limit, a database error, or a theme conflict. The developer must resolve the issue permanently without causing any data loss or downtime. Please only apply if you have proven experience fixing critical WordPress errors. Fast response and quick turnaround are highly appreciated.