My WP site is hacked.

Get a fresh cup of coffee, take a deep breath and carefully follow this guide. When you’re done, you may want to implement some (if not all) of the recommended security measures.

If you’re unable to clean your site(s) successfully, there are reputable organizations that can clean your sites for you. Sucuri and Wordfence are a couple.

Word fence doesn’t able to clean my site as the problem is with wp core file

Please read the guide I linked in my reply.

@speakingitout who is your hosting provider? If WordFence can’t clean core files, there’s a possibility your host restricts write access to core files. For example, Godaddy’s managed WordPress hosting does that. You would have to contact your hosting provider in that case.