hi seth, thanks for your comment. you're definitely not being dense!! this game is part of a particular niche culture of tabletop roleplaying game writing called "GM-less games", or "no dice no masters" games, and i can understand it being hard to access if this is your first crack at a GM-less game (and, in addition, i put a lot of myself into this game—it is a game about trans people hanging out and making art and living their lives together, and i can see how that might not be something accessible for just anyone.)
i'll answer your questions as best as i can, and if you'd like, i can leave some resources that might be helpful too.
i would describe girlfriend as a slice-of-life game about the magic in the everyday, the power of art and style, and a celebration of the happy warm feelings we feel when we connect to each other. (its also a game about werewolves i think thats a cool part of it too)
first, i wrote girlfriend to support a kind of roleplaying that i personally enjoy: its gameplay is pretty freeform (you can basically do whatever you want) and the mechanics really only exist to get you started, help you transition between scenes, and offer guidance for how to end your story.
for setting your scenes, it can be helpful to brainstorm some fast-and-loose details about your setting ("what if we set this story in fantasy london where everything's mostly the same but there are talking animals?" "what if we make our game like mob psycho?" "what if we set it in our city?" "what if we were all furries?" etc.) the intro section for each playbook can help guide this section, giving you some starting places for character-building.
once you have a few starting details for your world picked out, direct your attention to the "pick 1+ that is on my mind during my first scene" section for a few of the characters. you can use these to build your starting scenes — for example, maybe the EDM Witch has made a breakthrough on their project and is meeting up with the Band Lesbian, who is going somewhere and wants someone to come with them, because they're scared to go alone. this can be enough material to start a scene, especially if you take time to discuss with the other players and flesh out compelling details. (what breakthrough did i just make? where are you scared to go alone? this is a GM-less game, meaning it's a shared responsibility across the table to help brainstorm these details together!)
girlfriend is more freeform than a game like D&D (you have to decide your character's objectives — but the playbooks have tips to help guide you there!) and that means it's up to the players to decide where to start and end scenes. you might set one in a cafe and open on the characters meeting up, for example, and then end the scene after they've made a decision on what to do next, and cut away to different characters, or something like that.
i will say, too, that this is a slice-of-life game, meaning the scenes focus on what a usual moment in the characters' lives look like. it's okay to just have a scene where, for example, you're all hanging out and talking about life, or gossiping, or making something together, or maybe going somewhere together. a scene can just be describing an experience we share, and talking about how each of us is feeling during that shared activity.
in the end, i want to say it's okay if this game isn't a good fit for your group — it's definitely tailored to offer you a specific type of roleplaying experience, one that's silly, dreamlike, doodly, and that centers around trans people and their experiences. this isn't what everyone looks for in their games, and that's okay.
i hope this is helpful for you. if there's anything else i can help you out with, let me know.