James, thanks for your reply.
I’ve managed to get it working but i will definetly give your solution a try (and see which one runs better).
What i did was: i created a new loop with all listings that are in the category “restaurant”. Based on the results i created an array of ID’s.
In the main loop for the archive page i used the array i just created in the ‘post__in’ query variable and voila.
Would you say this consumes a lot of resources?
I’m trying to go about this as simple and smooth as possible so i’m definetly want to go with the best-practice.