I’m new to @PPlE and I need to learn the knowledge of its use, what can you recommend

How did your start this one? It is the same. Start with the "Ask the Community" link at the top right.

Not sure what @PPIE means. Can you expand on ht?

These forums are user to user for technical questions. We need something more than "learning to learn". So here is a link to a guide:

iPhone User Guide - Apple Support

FWIW, I have no clue what @PPiE is either. Please remember that these are worldwide forums and foreign speakers appreciate regular written English.