Thanks for asking and congrats on getting your internship!
I would say that the absolute best thing to do that will make you a better editor is practice. That might not sound that exciting but it’s been true for me. When I first started, I knew very basic editing techniques and it took a while before I felt comfortable to handle editing a project successfully on my own. The more you practice, the faster you get at editing. So like you said, you view a clip a billion times while you edit it, but the more you practice, the more your eyes and ears get tuned to editing, and it moves a lot quicker. It would take me twice as long to edit something when I first started than it would for me now.
Also, use keyboard shortcuts as much as you can. It really helps your speed and working through footage. If there’s someone you work with or a senior editor that wouldn’t mind you sitting in and watching them work, that’s also really good. When I first started, I watched Michelle edit all the time and it helped me immensely, and still does, and it’s basically how I learned most of what I know about editing now. If there isn’t anyone, then look up and watch as many tutorials as you can and practice things that you want to learn for fun.
Don’t put a lot of pressure on yourself to be great at editing when you’re first learning. It takes time but you’ll notice yourself getting better and faster at it. So have patience. Things that were difficult at first, you won’t even have to think about later on.
I don’t know if you make your own videos, but it serves as great practice for editing too.
ASK QUESTIONS! Even if you’re hesitant, it’s okay to ask for clarification on something or look something up. There was plenty I didn’t understand right away as I was learning. Jot down things that are difficult for you and practice those things specifically.
Try stuff that you think could be interesting. Follow your ideas. That’s what the undo button is for. Be creative with your editing and trust that you can change it if your idea doesn’t flow for some reason.
Overall, I would say, don’t worry about it too much. As long as you keep practicing and don’t give up, you’ll learn and pick up everything you need to. Just have fun and be creative with it! :D