After deploying website which things are able to website safe.

Well SSL is a must these days! You have a few options here.

1. Buy a certificate and add it to your server configuration. That depends on what system you use, nginx, apache, etc.
2. Use LetsEncrypt to generate a free certificate. It's important to know that you need to refresh this every 3 months (this can be done automatically)
3. Use CloudFlare. The have free certificates as well and DDOS protection. One important thing is that they need to manage your DNS settings as well.

If you're new to this I would go for option 3 ;)

SSL does nothing to protect your site... it protects your user's information from snoopers and spoofers.

The BEST thing you can do is to understand programming techniques that will create secure applications.

A good source for information is the https://owasp.org website, and their list of to 10 website vulnerabilities.

https://www.owasp.org/images/7/72/OWASP_Top_10-2017_%28en%29.pdf.pdf