The main problem is you don’t understand magic, at all. Most people who aren’t wizards don’t, you suppose, but that doesn’t really make things any easier on you.
What you’re thinking is that if you understood the limitations of the actual spells they could throw at you, you might be able to work around that. But you don’t. All you see right now is a floating door, and when you really think about it, you’re not even sure how that works. Is the wizard specifically moving the door, or is there some kind of field that makes things float? If you stood in front of it, would you float too? Would you float while the door came crashing down?
You’re not sure how useful it would really be to answer these questions, but it suddenly strikes you that answering them would be easier by putting something in front of the door that isn’t you. And that’s when you realize that you’ve got the horned helmet in your hands. You must have grabbed it off the gang member without thinking, and then you didn’t have time to hide it back in the costume.
So you toss it. And it lands on the floor. Well, you suppose that clarifies things a little, though you’re not sure how it helps you…
It does, however, give the wizard an idea of which side of the doorway you’re on, which you realize just in time to dodge the door as it flies towards you. It falls to the ground some distance away… maybe the spell can’t hold up that long, or over that much distance.
But you don’t have a lot of time to think about that. The wizard seems likely to step out to see how their little trick worked… and they’ll almost definitely be on guard, just in case it didn’t. You could take the risk of pressing an attack anyway, or you could use the time to run. Maybe even hide, though you haven’t got a lot of options there.
Whatever you do, you’ll need to do it quickly.
Hide behind the costume and/or run away!