Going back to basics again, and some in depth security?

Hello,

I'm on my 4th grade in my engineering circle this year, the 1st year was just overall basics, 2nd and 3rd I had decided to focus more on the Dev side (Web, mobile mostly), but after a few internships and some external work I decided that I liked Networking best.

Now since we have an upcoming internship, I wanted to go back to the basics quicky (last time I learned through CCNA).

Is there anything recommended for me? I want to go through the basics of networking again and learn more about security, should I stick to CCNA or is there anything else (I also watch some youtube videos to learn more about hardware, for exemple layer 3 switches and so on).

Thank you for your help and have a nice day