Bombing your first job interview is how you learn to prepare for the second. Almost everyone has a bad one.

A first interview is mostly a lesson in what interviews are. You find out that they ask about weaknesses, that they want examples rather than adjectives, that there is a silence you are supposed to fill. Nobody knows that in advance, which is why a bad first one is standard rather than a sign about your prospects.

Write down every question you were asked while you can still remember them. Prepare a short real example for each and say them out loud, to a person if possible. Then get the next interview booked, because the practice goes stale.