What's making you nervous OP? Is it the feeling you aren't going to have enough time to finish or are you worried the questions are going to be difficult?
If it's a time thing, know that if you are well versed in the material 2-3 mins per question is ample amounts of time. If you are spending more than 3 mins on a question you are doing something very wrong. So know that some questions will go faster than others and as long as you know the material well enough you will have enough time. While you do practice tests keep an eye on your pace. My pace is 30 mins for the first question leaving me 45 mins for the remaining 27 questions you can change that to whatever way you like, just make sure you have some sort of time management plan.
I've been in your exact situation before. What you are describing sounds like doesn't sound like anxiety has that big a role, it sounds more like you understand the basics really well but still have trouble applying them to much more difficult questions.
everything else felt like it was written in a language i don't speak. when i did understand the questions
This can mean 2 things and I have experienced them constantly. (1) Trouble translating what is being said into mathematical problem/ knowing how to setup the problem. (2) Reading the question too fast and not really grasping what it is asking you to do due to time pressure. Now this was common for me, it may not be your case but it's my 2 cents worth.
For situations where you feel you have no clue what the question is asking, especially on the ones that throw multiple scenarios at you, just take it in parts. Break it down to simpler terms and then solve the question. I would constantly try to understand the question in one shot, never worked on the much more difficult ones-- 700 level questions.
Other than that, slow down.. read and re-read if required.. practice now on the prep to be able to decipher questions. The math is always going to be easy, the key do doing well is to be able to understand on a mathematical level what the question is asking you.