question #3 Sahih Muslim 602d, Book 5, Hadith 197 : What should a person do if they miss part of the prayer led by the Imam?

The Messenger of Allah (ﷺ) said: When the words of Iqama are pronounced, none of you should run to it (to join the prayer) but walk with tranquillity and dignity, and pray what you are in time for and complete what has gone before (what the Imam has completed).