i meant a5 and i went to b5 sorry
En passant Question

En Passant
The last rule about pawns is called “en passant,” which is French basically means “in passing”. If a pawn moves out two squares on its first move, and by doing so lands to the side of an opponent’s pawn (effectively jumping past the other pawn’s ability to capture it), that other pawn has the option of capturing the first pawn as it passes by. This special move must be done immediately after the first pawn has moved past, otherwise the option to capture it is no longer available. Click through the example below to better understand this odd, but important rule
Its written in Learn > Chess Rules & Basics > Special cases or something like that

It helps to know why en passant was introduced. Originally, pawns could only move one square, including the first move. The two-square first move was introduced only to speed up the game. However, this enabled pawns to evade capture (as you seemed to be trying to do). En passant (taking in passing) stopped this, while still speeding up the game.
so, in the diagram, if Black moves ...b5, then White has en passant, ie: axb6.
I play Black, I have K on b8 and pawns on b7 and a7, my opponent has a pawn on a6, I move my b pawn to b5, he hinks he should be able to take it en passant,
I thought it was only if for example if he was on a6 and I went b5 in this scenario am i wrong?