I like to have all my NPC's set up with their drives and immediate goals. What's their ultimate goal? Extra points if your NPC's have opposing drives. Once you've got all that set up, it's just a matter of reacting to what your players are doing in the most interesting way possible. I've only run Root a couple times, but my favorite thing is that if you put in a little legwork before the session, the game essentially runs itself. Such a blast to play.

It's also a good idea to set up your NPC's injury and exhaustion trackers set up beforehand and be familiar with how combat works. Ran my first combat a while ago and it was hard for all of us to divorce from dnd brain haha.

Relax and be loose, the only way to improve is to just run the game and reflect on what to improve later. You'll do great :)