Steps to do when you use cloudflare to hide your server's ip address

Follow the steps; the main concept is to block any other IPs if you’re using CF.

remember to delete nginx rules of ufw first.

disable ping request:
sudo nano /etc/sysctl.conf

add the following line:
net.ipv4.icmp_echo_ignore_all = 1

reflect the change:
sysctl -p