How to stay calm for a 7 minute scientific research talk?
(For context: I am a mathematician in the U.S.) For many reasons, I make my research students "rehearse" their presentations many, many times. It is of course all the more challenging to have a ridiculously short time in which to say anything. So, yes, crazy choices must be made. A more experienced person could coach/advise you on what to leave out.

Crazily-enough one of my students has won some presentation prizes for super-short talks by ... as she and I said to each other... "leaving out all the math". Definitely as opposed to trying to cram toooo much in.

Do not think in terms of giving a lecture for students. The only sane way to give such a short presentation is to think in terms of addressing people who already know enough so that the new parts of your work can stand on their own. It is obviously impossible to explain almost anything at all. No "background" on basic grad-level material. No time!

So, absolutely, find a more senior person to "rehearse" with. Your own peers may not have a clear-enough idea of what should be included to really help you. "Experts know what experts know."

(And, to be clear, rehearse the talk over and over and over and over... with your coach/advisor/critic... until you can do it in your sleep, etc.)