how to move pawns
That 2 move jump pawns can do, it can't be used to avoid offering a pawn trade. The other player is able to capture as if the pawn had only moved 1 square. I find this the shortest explanation.
THE PAWN MUST HAVE MOVED TWO SQUARES THE MOVE BEFORE THE CAPTURE.
You cannot delay en passant.
Pawn Play and Structure - for Beginners and Beyond…
https://www.chess.com/blog/RussBell/chess-books-on-pawn-play-and-structure
https://www.chess.com/blog/RussBell