Displaying products based on specific product property

[CSSOL]

Hello everybody,

I have the following problem:
I have added a self-defined property (boolean) that can be maintained per product. The aim should be that visitors (not logged in) shouldn't see all the products.

That means:
If the property is true, then the visitor of the shop sees the product.
If the property is false, then the visitor of the shop doesn't see the product. Only when he is logged in the product should be displayed.

Unfortunately, I am currently a bit in despair. Adding the property was not a problem. As I understand it, I have to adjust the search query in the category view. Unfortunately, I do not understand how. Can someone help me?

Thanks in advance.