Red Hat command returns, “-bash: sudo: command not found”

That tutorial seems odd. There is utterly no reason to use sudo with git since all Git is really is a version control system. So I believe your core problem is Git is not installed on your system to begin with. To solve that just coect to your server via SSH and run this command:

sudo yum install git-all

Then once Git is installed try ruing this command to clone the “Let’s Encrypt” tutorial; same command as their first command but without sudo:

git clone https://github.com/letsencrypt/letsencrypt

The follow the rest of the instructions on that tutorial and I’m pretty sure you will be all good to go!