My physics and chem teacher is so confusing

Well, as I said, my physics/chem teacher is super confusing. Like, she's supposed to give us classes and explain stuff but she seems like she's actively thinking while talking to us, so during her classes, especially when we're taught all classmates at once (we sometimes have physics classes with half of the class, it was meant for when we wanna make experiment since there wouldn't be enough materials/devices to use for everyone), the period is basically her explaining things with butchered sentences while she figures out what to say. µ

Obviously that leads to ppl getting distracted and chatty, plus I have particularly loud classmates this year, so not only do we get biutchered explanations but its also interruped with the teacher trying to silence everyone to speak. 

During exercices or demonstrations it's even worse, because we have to deal with this overall nonsense while she's correcting stuff and answering questions. So there will be this distracted mess of students, a confused teacher figuring our her shit on the board, and then she asks for the answers of a question out of nowhere. Obviously, me and my friends being part of the little people who stays at least a little bit focused, we have to answer or she'll get mad at everyone for being distracted.

So, the current chapter we're working on is no different, yet I have a test tomorrow that was announced friday. I'm very much worried about this test, which doesn't happen often, because although I already saw this chapter last year, she somehow made it quite confusing.