How do I stay calm at the front desk when it gets busy?

You can run the desk on a normal day. It is the full lobby, three phones, and two problems at once that swamps you. That is not a sign you are bad at this. It is the hardest part of the job, and it rattles almost everyone at first. When everything hits at once, your mind tries to hold all of it and freezes. The fix is not to move faster. It is to handle one thing fully, then the next. The people waiting can wait a moment longer than your panic tells you they can. Next rush, take one breath and say to yourself: one at a time. Greet the person in front of you, then the phone, then the next. You cannot do five things at once. No one can. You can only do the next thing well, and that is enough.