The audio here is generated speech. A recorded human voice for this lesson is on the way.
The two sounds
B and P are made in exactly the same place: both lips closed, then opened with a small puff of air. The only difference is your voice. For B your vocal cords vibrate while your lips are closed; for P they stay silent and the air comes out harder. Put two fingers on your throat and say "buh" then "puh". You feel a buzz on B and nothing on P.
The mistake learners make is not the mouth, it is the air. English P at the start of a word has a strong puff; hold a piece of paper in front of your lips and "pen" should move it while "Ben" barely does. If your P is too soft, English speakers hear B, and "pear" becomes "bear".
Hear the difference
Tap each word. Then test your ear.
At the end of a word the difference is mostly the vowel: the vowel before B is a little longer.
Say it out loud
Tap a sentence to hear it. Say it after the voice.
Practice · 3 min
Listen to each sentence, then say it back. Exaggerate the puff on every P the first time, then relax to normal. Record the last sentence and check that "park", "past" and "bakery" are three clearly different starts.
Say it today
Use it once in a real conversation before tomorrow. Out loud counts, even to yourself.