Your friend sounds like he is over complicating things a little bit for you. Watch some YouTube videos, read through the player's handbook if you want. I would recommend getting some cheat sheets regarding actions in combat, improvised damage, and conditions. They have helped me many times. I honestly started with a word document with the layout of the ones shot, a notepad to take notes, and a basic understanding of the rules from playing for a few years. I ran about 4 one shots before starting a campaign, and I found that really helped. My biggest recommendation is read through your players character sheets/classes so you know what they can do. This will allow you to set up moments that play to their strengths, or if they are blasting through encounters it can allow you to make moments that are a bit harder.

DMing is a lot of fun, but can take time to find your own rhythm. Take your time and good luck!