@MJG017 I did all of the methods that I've followed from the guide step-by-step, including holding down the option key button method but still nothing has happened or showed up. I wonder if this has to do with the type of external hard drive that I'm using? 

This is the one that I've bought and am using, as I've spoke with a customer service representative on JB-HIFI almost a week ago as he also studied I.T in the past and is very familiar with it. He recommended me to use this one specifically so I bought it.

Samsung T7 Portable SSD Drive [1TB] 

I know that external hard drive and SSD are pretty different (as far as I know, if im correct) but I did tell him that I needed an external hard drive (to help install Ubuntu on my MacBook and all) specifically but yea according to him he recommended that I use an SSD drive.

Thanks - I was thinking of doing computer science (bachelors) after I complete my certificate (IF I'll be able to get the offer once I complete the certificate) - but according to my university's student connect customer service people, that would mean I would have to do either a bachelor of I.T or cybersecurity for the first 6 months before I transition into doing bachelor of CS. Why I'm thinking of computer science is mainly because the other day I was doing some research on what degrees/fields to do for someone who has really bad social anxiety and stuff, and a few people have mentioned computer science (well thats part of  the main reason why I chose to study I.T. Also, because I've always been using technology myself throughout the majority of my life lol) so I thought, hmm... 

do you think computer science would involve programming? 😳