How do I check a player for a specific item?

[einsReplex]

Hey
I would like to know how
I can check a player for a specific item?

And that if you press a button you
don't just get an item but if I click again I want to get this item again. How does that work?

I would be happy to receive an answer

 

[PetteriM1]

Check for a specific item where?

 

[einsReplex]

So at Brick, it should be taken away if I buy a stick,
for example, and if I already have one, you should be able to buy one, but not that the other
one who you bought before twists

 

[einsReplex]

The item that was then bought from the shop should
also go to the slot where the brick went