I appreciate if someone helps me to secure my website from being hacked. Is there any helpful plugin to use?
Start in the Codex: https://codex.wordpress.org/Hardening_WordPress .
Basically, strong passwords on all accounts (hosting, FTP, email, WP users), and ensuring updates on WP/Theme/Plugins are done regularly.
Also, carefulness with themes and plugins you use. Look at the support areas of both for other's issues. Consider avoiding themes/plugins that have not been updated lately, or don't have answers to support questions from the author.
And, hosting security: PHP versions, etc. And, regular backups of data and files.