Nginx Security Guide

Hi to all, I am new to Nginx and I have been tasked to change the security settings of my company's website.

My current ngix.conf file (It is running on Centos 7) is as shown in the attached document. And I would like to change the security settings as per recommended within https://cipherli.st/

My question is:
1. If I were to change the settings, do I need to make any changes to the .crt and .key file? If yes, what do I need to do?
2. After updating, do I need to restart all services?
3. Any other stuff that I should look out for or do?

Any help will be much appreciated!