Getting 404 error page when publishing, updating, drafting a post

In my site i was redirecting to “https://geeksail.com/wp-admin/post.php” url and its showing 404 error when i was trying to write a post, or drafting, updating it. Its a newly started blog so I re-installed the wordpress, but again getting same problem. But when I write only post title without content, its getting published.. Can you please help me to find this?