If the intruder has already broken in, retreat into your home - put other doors between the two of you. Memorize a description of the intruder. When they have left, write it down as soon as you have called the police. Don't rely on memory. If you find any evidence that someone has entered your home or apartment, report it even if nothing has been taken.
Illegal entry is a crime.
Never get between a burglar and the exit, and never try to stop them from leaving.